Interpeduncular Nucleus

Because high densities of alpha3beta4 nicotinic receptors occur in the medial habenula and the interpeduncular nucleus and moderate densities occur in the dorsolateral tegmentum, ventral tegmental area, and basolateral amygdala, the present study was conducted to determine if 18-MC could act in these brain areas to modulate methamphetamine self-administration in rats. In contrast, local administration of 18-MC and the other antagonists decreased sucrose self-administration when administered into the dorsolateral tegmentum or basolateral amygdala but had no effect when infused into the medial habenula, interpeduncular nucleus, or ventral tegmental area.  

Besides to their brainstem location where I1-receptor sites play a significant role to regulate and modulate blood pressure, they also are found in different parts of brain with the highest densities in the striatum, pallidum, hippocampus, amygdala, substantia nigra, while I3-receptor sites were revealed in pancreas which enhances insulin secretion, I2-receptors are widely distributed in interpeduncular nucleus, arcuate and pineal gland and take a part in monoamine turnover.  

LGR8 was also detected throughout the medial habenula-fasciculus retroflexus-interpeduncular nucleus pathway, further indicating that the receptor is transported from mRNA-expressing soma to remote axonal/terminal sites.  

On the other hand, morphine was shown to alter the neurochemistry of the habenulo-interpeduncular pathway, inducing biphasic changes in acetylcholine release in the interpeduncular nucleus. Nicotine (0.1 and 0.4 mg/kg s.c.) produced a dose-dependent decrease in extracellular levels of acetylcholine, while methamphetamine (1 and 4 mg/kg i.p.) produced an increase in acetylcholine release in the interpeduncular nucleus.  

As to more generalized influences, the effect of gonadal steroids on the GFAP-reaction interpeduncular nucleus, an area not involved in hormonal regulatory mechanisms was studied.  

This minireview examines the roles of various nicotinic receptors in the mechanisms of nicotine dependence, discusses the potential role of the habenula-interpeduncular nucleus axis in nicotine withdrawal, and highlights nicotinic receptors containing the beta4 subunit as a potential pharmacological target for smoking cessation strategies..  

Habenular projection neurons on both sides of the brain share a stereotypical unipolar morphology and elaborate remarkable spiraling terminal arbors in their target interpeduncular nucleus, a morphology unlike that of any other class of neuron described to date.  

Furthermore, the sections are collected at an equal distance, 200 mum instead of 400-500 mum used previously, thus enabling the use of virtual z-stacks and three-dimensional (3D) volume renderings to investigate differential localization patterns in much smaller brain structures such as the substantia nigra and the interpeduncular nucleus.  

In all vertebrates, axons from the medial habenular nuclei project within a prominent fiber bundle, the fasciculus retroflexus, to a shared midbrain target, the interpeduncular nucleus of the ventral tegmentum.  

18-Methoxycoronaridine, an agent that reduces morphine self-administration and attenuates dopamine sensitization in the nucleus accumbens in response to repeated morphine, has been shown to produce these effects by acting in the medial habenula and interpeduncular nucleus. Acetylcholine, one of the predominant neurotransmitters in the interpeduncular nucleus, may be a major determinant of these interactions. To determine if and how morphine acts in the interpeduncular nucleus, the effects of acute and repeated administration of morphine on extracellular acetylcholine levels in this brain area were assessed. Acutely, morphine produced a biphasic effect on extracellular acetylcholine levels in the interpeduncular nucleus such that low and high doses of morphine (i.e., 5 and 20mg/kg i.p.) significantly increased and decreased acetylcholine levels, respectively.  

While there are very low densities of alpha3beta4 nicotinic receptors in the mesolimbic pathway, these receptors are prominently localized in the medial habenula (MHb) and in the interpeduncular nucleus (IPN).  

Strong labeling was observed in the whole olfactory system, cortical layer VII, hippocampus, hypothalamus, cerebellum, habenula, fasciculus retroflexus, and interpeduncular nucleus in adults.  

The lateral habenula is the principal actor in this direct dialogue, while the medial habenula mostly conveys information to the interpeduncular nucleus before this modulates further regions.  

The fasciculus retroflexus and its termination in the mesencephalic interpeduncular nucleus were also densely labeled.  

The medial habenular nuclei of the zebrafish diencephalon, which lie bilateral to the pineal complex, exhibit left-right differences in their neuroanatomy, gene expression profiles and axonal projections to the unpaired midbrain target--the interpeduncular nucleus (IPN).  

The habenular neurons on both sides of the zebrafish diencephalon show an asymmetric (laterotopic) axonal projection pattern into the interpeduncular nucleus.  

(4) The antigen is distributed only in limited areas of the brain, namely in the periphery of the forebrain, the hypothalamus, the optic tectum, the interpeduncular nucleus, the cerebellum and the ventricular rim of the medulla.  

[ (125)I]mAb 299 labeling was nearly eliminated in beta2(-/-) sections, although dorsal interpeduncular nucleus (IPN) retained a faint signal.  

Examination of cholinergic axon terminals in known target areas of BF projections indicated that the basolateral amygdaloid nucleus contained numerous terminals co-immunoreactive for ChAT and VGLUT3, whereas sampled areas of the olfactory bulb, neocortex, hippocampus, reticular thalamic nucleus, and interpeduncular nucleus were devoid of double-labeled terminals.  

At metamorphic climax and in newly metamorphosed frogs, positive perikarya were found in the striatum and in the interpeduncular nucleus.  

Affected were visual and auditory structures, frontal cortex, amygdala, hippocampus, nucleus accumbens, caudate-putamen, interpeduncular nucleus, and substantia nigra.  

NPW-ir fibers were observed in several brain regions, including the lateral septum, bed nucleus of the stria terminalis, dorsomedial and posterior hypothalamus, central amygdaloid nucleus, CA1 field of hippocampus, interpeduncular nucleus, inferior colliculus, lateral parabrachial nucleus, facial nucleus, and hypoglossal nucleus.  

Because alpha3beta4 nicotinic receptors in the brain are preferentially located in the medial habenula and the interpeduncular nucleus, the present study was conducted to determine if 18-MC could act in these brain areas to modulate morphine self-administration in rats.  

Six hours after intracerebroventricular microinjection of MnCl2, T1-weighted 3D MRI (2.35 T) at 117 mum isotropic resolution revealed a continuous pattern of anterograde labeling from the habenula via the fasciculus retroflexus to the interpeduncular nucleus.  

Autoradiography also revealed the presence of 5-HT 1A receptor binding sites in the cortex and in the interpeduncular nucleus, due to its greater sensitivity and spatial resolution compared with PET imaging.  

The rats did not self-administer nicotine into surrounding regions including the anterior VTA, substantia nigra, the region just dorsal to the posterior VTA, interpeduncular nucleus, or medial mammillary nucleus.  

The fasciculus retroflexus and its termination in the mesencephalic interpeduncular nucleus are prominently stained.  

To test this possibility, 18-MC was locally administered into the medial habenula, interpeduncular nucleus and locus coeruleus of morphine-dependent rats; this treatment was followed by naltrexone to precipitate a withdrawal syndrome. Some doses of 18-MC administered into the interpeduncular nucleus significantly ameliorated rearing, teeth chattering, and burying, while other doses exacerbated diarrhea and teeth chattering.  

We detected strong hybridization signals in cell bodies located in the internal plexiform layer of the olfactory bulb, the interpeduncular nucleus of the midbrain, the ventral and dorsal tegmental nuclei, the median raphe nucleus of the pons, the ventral part of the medullary reticular nucleus, the ventral horn in the spinal cord of both rats and mice, and in a few Purkinje cells of rats, but not of mice.  

In other regions, immunoreactive cells are moderately stained (i.e., magnocellular nucleus of the posterior commissure, amygdaloid nucleus, interpeduncular nucleus, lateral periaqueductal gray) or weakly stained (i.e., vascular organ of the lamina terminalis, hippocampus, inferior colliculus, reticular nucleus).  

Under the influence of Nodal signaling, positioning of the parapineal sets the direction of habenular asymmetry and thereby determines the left-right origin of habenular projections onto the midbrain target, the interpeduncular nucleus (IPN).  

In contrast, spinal cord injury (SCI) resulted in strain-specific changes in forebrain activation categorized by structures that showed significant increases in: (1) only LE SCI rats (posterior, ventrolateral, and ventroposterolateral thalamic nuclei); (2) only SD SCI rats (anterior-dorsal and medial thalamus, basolateral amygdala, cingulate and retrosplenial cortex, habenula, interpeduncular nucleus, hypothalamic paraventricular nucleus, periaqueductal gray); or (3) both strains (arcuate nucleus, ventroposteromedial thalamus, SI and SII somatosensory cortex).  

The habenula and interpeduncular nucleus (IPN) are part of a dorsal diencephalic conduction system which receives input from cholinergic, striatal, and hypothalamic areas, and sends output to several, disparate midbrain regions.  

Moreover, significant amounts of specific 125I-hPP binding were observed in the medial preoptic area, paraventricular nucleus of the hypothalamus, interpeduncular nucleus, and various brainstem nuclei, even after masking Y4 and Y5 receptors.  

Chronic administration of high doses of nicotine results in axonal degeneration in the central core of the fasciculus retroflexus, a fiber tract connecting the habenulae (Hb) to the interpeduncular nucleus (IPN).  

Lesions of habenula were confirmed histologically and neurochemically by reduction of choline acetyltransferase in the interpeduncular nucleus.  

iKEPI fiber/terminal patterns are relatively densely distributed in striatum, nucleus accumbens, septum, bed nucleus of the stria terminalis, hippocampus, paraventricular thalamus, ventromedial hypothalamus, interpeduncular nucleus, raphe nuclei, nucleus caudalis of the spinal tract of the trigeminal and dorsal horn of the spinal cord. iKEPI-positive cell bodies lie in the nucleus accumbens, striatum, lateral septal nucleus, granular layer of dentate gyrus, interpeduncular nucleus, dorsal root ganglia and cerebellar vermis.  

Here we investigated a possible source of such modulation, the midbrain interpeduncular nucleus, by monitoring immediate early genes and synaptic activity.  

The habenulae are part of an evolutionarily highly conserved limbic-system conduction pathway that connects telencephalic nuclei to the interpeduncular nucleus (IPN) of the midbrain .  

5-Iodo-A-85380 was markedly less potent at eliciting [ 3H]ACh release from rat interpeduncular nucleus synaptosomes, [ 3H]noradrenaline release from rat hippocampal slices, and Ca2+ increases in a cell line expressing rat alpha3beta4 nAChR (EC50 = 5, 3.2, 1.6 microM, respectively).  

The NPY-ir cells were detected in the dorsal and ventral rostral midbrain and the interpeduncular nucleus by 21 weeks and 32 weeks of gestation, respectively.  

The highest density of immunoreactive fibers containing methionine-enkephalin-Arg(6)-Gly(7)-Leu(8) was found in the spinal trigeminal nucleus, the central gray and the reticular formation of the medulla oblongata, pons and mesencephalon, the solitary nucleus, the spinal vestibular nucleus, the dorsal accessory olivary nucleus, the raphe obscurus, the substantia nigra and in the interpeduncular nucleus.  

Labeled neurons were counted in the suprachiasmatic nucleus, posterior tuberculum, interpeduncular nucleus, and locus coeruleus, and correlation between neuronal numbers and behavioral scores was tested. The number of catecholaminergic neurons decreased with increasing 6-OHDA concentration in the suprachiasmatic nucleus, posterior tuberculum, and interpeduncular nucleus.  

Nicotine-treated animals had a significantly higher maximal efflux in cerebral cortex and superior colliculus, but not in thalamus or interpeduncular nucleus plus medial habenula. Binding was significantly increased after 2 weeks nicotine exposure in cortex, superior colliculus and thalamus, but not in interpeduncular nucleus plus medial habenula.  

There were no significant effects in the pineal gland or interpeduncular nucleus which, like the arcuate nucleus and area postrema, are rich in I(2) sites.  

Efferent projections of the ventral telencephalon terminate in the supracommissural nucleus of area ventralis telencephali, the posterior zone of area dorsalis telencephali, habenula, periventricular pretectum, paracommissural nucleus, posterior dorsal thalamus, preoptic region, midline posterior tuberculum (especially the area dorsal to the posterior tuberal nucleus), tuberal (midline) hypothalamus and interpeduncular nucleus.  

Assay of choline acetyltransferase (ChAT) in the interpeduncular nucleus terminal region of the habenulo-interpeduncular tract, showed marked reduction (by 80%) in habenula-lesioned animals.  

RESULTS: The autoradiographic results showed that (123)I-ADAM accumulated in SERT-rich brain areas after systemic injection, including the globus pallidus, thalamus, hypothalamus, substantia nigra, interpeduncular nucleus, amygdala, and raphe nucleus.  

Changes in four major brain systems are suggested to underlie susceptibility to helplessness and possibly depression: (a) an unbalanced prefrontal-cingulate cortical system, (b) a dissociated hypothalamic-pituitary-adrenal axis, (c) a dissociated septal-hippocampal system, and (d) a hypoactive brain reward system, as exemplified by a hypermetabolic habenula-interpeduncular nucleus pathway and a hypometabolic ventral tegmental area-striatum pathway.  

The mGlu1 receptor is also present in variable degree in the dorsal lateral septal nucleus, amygdala, interpeduncular nucleus and median raphe nucleus.  

Neurons containing VGLUT3 transcript are essentially observed in the caudate-putamen, the olfactory tubercle, the nucleus accumbens, the hippocampus, the interpeduncular nucleus and the dorsal and medial raphe nuclei. The distribution of the VGLUT3 protein, as determined with specific antisera, overlaps with that of the transcript in the caudate-putamen, olfactory tubercles, hippocampus, cortex, interpeduncular nucleus, and raphe nuclei, suggesting that VGLUT3 is essentially present in local projection neurons in these regions. Furthermore, co-localization studies indicate that VGLUT3 is present in GABAergic interneurons in the hippocampus, as well as in the interpeduncular nucleus.  

The expression of Fos protein in 5-HT-containing neurons (5-HT/Fos co-localized neurons) could be observed in the ventrolateral subdivision of the midbrain periaqueductal grey, interpeduncular nucleus, paramedian raphe nucleus, all of the brainstem raphe nuclei, the alpha part of the gigantocellular reticular nucleus and the lateral paragigantocellular reticular nucleus.  

Prominent immunostaining included: 1) the medial habenula, efferents composing the fasciculus retroflexus, and the interpeduncular nucleus; 2) nuclei and ascending tracts of the auditory system inclusive of the medial geniculate; 3) the sensory cortex barrel field and cell bodies of the ventral thalamic nucleus; 4) olfactory-associated structures and the piriform cortex; and 5) sensory and motor trigeminal nuclei.  

However, other data indicate that the habenular cells were labeled by spread of the tracer from the BON to the adjacent fasciculus retroflexus and interpeduncular nucleus.  

The dentate nuclei and central tegmental tracts were involved in two cases each (all instances), and the putamina, interpeduncular nucleus, and pallido-cortical-nigro-cortical tracts in one.  

DISC1 expression is highly localized, with most prominent expression in the dentate gyrus of the hippocampus and lateral septum, and lower levels of expression in the cerebral cortex, amygdala, paraventricular hypothalamus, cerebellum, interpeduncular nucleus, and subthalamic nucleus.  

In addition, the level of epibatidine labeling was very high in the epithalamic nuclei and the interpeduncular nucleus, whereas labeling by nicotine and cytisine was very weak in the same regions.  

The neuroanatomical findings provided the initial demonstration that olfactory information is conveyed from the olfactory bulb to the hypoglossal nucleus via the interpeduncular nucleus (IPn) by both fast disynaptic and different polysynaptic pathways.  

In addition to the nuclei mentioned above, the highest densities of such immunoreactive fibers were located in the spinal trigeminal nucleus, the lateral reticular nucleus, the nucleus of the solitary tract, the superior colliculus, the substantia nigra, the nucleus ambiguus, the gracile nucleus, the cuneate nucleus, the motor hypoglossal nucleus, the medial and superior vestibular nuclei, the nucleus prepositus hypoglossi and the interpeduncular nucleus.  

The results indicated that congenitally helpless rats had 64-71% elevated metabolism in the habenula and a 25% elevation in the related interpeduncular nucleus.  

We previously demonstrated that in rat, astrocytic glial fibrillary acidic protein- (GFAP) expression in the interpeduncular nucleus (IPN) was responsive to testosterone and in females the intensity of GFAP-immunoreactivity (IR) followed the periodic hormonal changes of the estrous cycle.  

Carbachol was not reliably self-administered into a site just dorsal to the VTA or into the adjacent substantia nigra and was self-administered only weakly into the adjacent anterior VTA or interpeduncular nucleus.  

In the brainstem, the central gray, interpeduncular nucleus, secondary visceral region of the isthmus, rhombencephalic raphe, inferior olive, vagal lobe, and Cajal's commissural nucleus were all richly TRHir-innervated.  

In addition, immunoreactive fibres were observed in the septum, amygdala, lamina terminalis, supraoptic nucleus, nucleus of the paraventricular organ, ventromedial hypothalamic nucleus and interpeduncular nucleus.  

Autoradiography revealed that the highest levels of binding were in the arcuate nucleus, interpeduncular nucleus, area postrema, pineal gland and ependymal cell layer lining the ventricles.  

In the presence of glutamate receptor antagonists, bicuculline-sensitive spontaneous GABA inhibitory synaptic currents (IPSCs) could be readily resolved in whole-cell recordings from neurons in the interpeduncular nucleus (IPN) maintained as brain slices.  

in axons from medial habenula through the core of the tract to interpeduncular nucleus.  

Further TRHir neurons were observed in the interpeduncular nucleus. The medial and lateral mesencephalic reticular areas and the interpeduncular nucleus were richly innervated by TRHir fibers.  

The beta2 nicotinic acetylcholine receptor subunit null mutation eliminated most high affinity [ (3) H]epibatidine binding in mouse brain, but significant binding remained in accessory olfactory nucleus, medial habenula, inferior colliculus and interpeduncular nucleus. Residual [ (125) I]epibatidine binding sites in the inferior colliculus and interpeduncular nucleus were subsequently characterized. Most acetylcholine-stimulated (86) Rb(+) efflux is eliminated in thalamus and superior colliculus of beta2 null mutants, but significant activity remained in inferior colliculus and interpeduncular nucleus.  

Retrogradely radiolabelled neurons in various numbers were detected in several brain regions including medial septum-diagonal band complex, lateral septum, rostral part of medial and lateral preoptic areas, lateral habenula, ventral premammillary nucleus, apical subregion of interpeduncular nucleus, laterodorsal tegmental nucleus, and dorsal and median raphe nuclei.  

In brief, very high levels of Y1R-LI were seen in the islands of Calleja, the anterior olfactory nucleus, the molecular layer of the dentate gyrus, parts of the habenula, the interpeduncular nucleus, the mammillary body, the spinal nucleus of the trigeminal, caudal part, the paratrigeminal nucleus, and superficial layers of the dorsal horn.  

DNPI immunoreactivity was much more intense than VGluT1 immunoreactivity in many brainstem and spinal cord regions, except the pontine nuclei, interpeduncular nucleus, cochlear nuclei, and external cuneate nucleus.  

Moderate densities appeared in the arcuate nucleus (Ar), median eminence, entopeduncular nucleus, ventral tegmental area, retrorubral area, periaqueductal central gray, interpeduncular nucleus and lateral parabrachial nucleus.  

A single acute pre-treatment with tranylcypromine significantly increased imidazoline I(2) site-specific binding in four regions: arcuate nucleus, interpeduncular nucleus, pineal gland and area postrema, but effects in cortical areas and cerebellum were not significant.  

A possible localization to axon terminals of 5-HT(2C) receptors is suggested by the disagreement observed in some regions such as septal nuclei and horizontal limb of the diagonal band (presence of mRNA with apparent absence of binding sites) and interpeduncular nucleus (presence of binding sites with apparent absence of mRNA).  

Nicotine increased the Fos IS in cortical, limbic and hypothalamic areas by 2-10-fold, and in the interpeduncular nucleus as well as in the visual areas the increases were 15-150-fold.  

Mismatching was found in the habenular nucleus, the commissura habenularis, the fasciculum retroflexus, and the interpeduncular nucleus, which contained high levels of binding sites but were devoid of ANF-immunoreactive structures.  

Lower levels of GFP were seen in olfactory periglomerular cells, neurons in the interpeduncular nucleus, and superior colliculus neurons.  

Attempts to mimic synaptic delivery of acetylcholine (ACh) with brief, repetitive pulses of high concentration ACh at synapses of medial habenula (MHN) and interpeduncular nucleus (IPN) neurons in vitro elicited temporally distinct facilitation and inhibition of glutamate secretion via nicotinic and muscarinic ACh receptor-mediated pathways, respectively.  

The intensity of immunostaining for the glial fibrillary acidic protein (GFAP) is outstandingly high in the interpeduncular nucleus. Since the interpeduncular nucleus is a hormonally inactive brain area where gonadal hormones do not induce plastic synaptic changes, it is concluded that concerning this astroglial marker a sexual dimorphism exists also outside the "endocrine brain"..  

As previously reported, CCK-A receptors were located throughout the area postrema, interpeduncular nucleus and nucleus tractus solitarii; however, binding to CCK-A receptors was also visualised throughout the medial pre-optic area, the arcuate nucleus and the circumventricular regions of the ventral hypothalamus, regions known to contain CCK-A receptors but which were previously undetectable using autoradiography in rat brain..  

One group of immunopositive neurons projected toward the interpeduncular nucleus (IPN), especially to the intermediate and the central subnucleus (type 1 neuron).  

In the midbrain, GAL-ir neurons appeared in the pretectal olivary nucleus, oculomotor nucleus, the medial and lateral lemniscus, periaqueductal gray, and the interpeduncular nucleus.  

The dorsal region of the rat interpeduncular nucleus (IPN) was found highly immunoreactive for vasoactive intestinal polypeptide (VIP).  

Among these regions, SCG, interpeduncular nucleus (IPN) and pineal gland showed the highest levels of alpha 3 protein expression.  

This study investigated the effect of electrolytic or neurotoxic lesions of two mesencephalic regions [ tegmentum (TEG) and interpeduncular nucleus (IPN)] on the latency and duration of TI (induced by postural inversion and by movement restriction) and on the latency of the motor response to a nociceptive stimulus (hot plate) in toads.  

They were distributed around the interpeduncular nucleus.  

High concentrations of Y1 immunoreactivity were found in the claustrum, piriform cortex (superficial layer), arcuate hypothalamic nucleus, interpeduncular nucleus, paratrigeminal nucleus, and lamina II of the spinal trigeminal nucleus and entire spinal cord.  

Caudal VLG projections innervate the lateral posterior nucleus, the anterior pretectal nucleus, the intermediate and deep gray of the superior colliculus, the dorsal terminal nucleus, the midbrain lateral tegmental field, the interpeduncular nucleus, the ventral pontine reticular formation, the medial and lateral pontine gray, the parabrachial region, and the accessory inferior olive.  

Many cells of the habenula were faintly ChAT-ir, but the neuropil of the interpeduncular nucleus showed intense ChAT immunoreactivity.  

Acetylcholine release stimulated by nicotinic agonists was measured as radioactivity released from perfused synaptosomes prepared from mouse interpeduncular nucleus (IPN) that had been loaded with [ (3)H]choline.  

Allylnitrile induced changes in the immunolabelling of GABA in the medial habenula, interpeduncular nucleus, substantia nigra, dorsal raphe nucleus and median raphe nucleus; the amount of immunolabelling decreased in all of these brain structures except the medial habenula at 2 days postdosing, and increased in all of these structures at 14 days postdosing. The present results suggest that the GABAergic systems through the medial habenula-interpeduncular nucleus-ascending raphe nuclei relay and through the substantia nigra may be involved in allylnitrile-induced behavioral abnormalities..  

In the isthmus, TRH was observed in cells of the interpeduncular nucleus, the nucleus isthmi, the dorsolateral tegmental nucleus, the superior reticular nucleus, and the central gray, although perikarya were TRHir only in alevin and/or juvenile stages. The interpeduncular nucleus and the secondary gustatory nucleus contained many TRHir fibers.  

In the three species, the NK3 receptor was similarly distributed within the cerebral cortex, the zona incerta, the medial habenula, the amygdaloid complex, the superior colliculus and the interpeduncular nucleus.  

Less dense binding was observed in the medial pallium, the thalamic region, the hypothalamus, the optic tectum, and the interpeduncular nucleus.  

Ex vivo autoradiograms of rat brain sections (120 min after iv injection of [ (125)I]ADAM) showed intense labeling in several regions (olfactory tubercle, lateral septal nucleus, hypothalamic and thalamic nuclei, globus pallidus, central gray, superior colliculus, substantia nigra, interpeduncular nucleus, dorsal and median raphes, and locus coerulus), which parallel known SERT density.  

Whereas no CYP2C11 or CYP2C12 immunoreactivity was detected in the basal ganglia of either male or female rats, marked CYP2C13 immunoreactivity was evident in neurones of the subthalamic nucleus, substantia nigra, and interpeduncular nucleus.  

Nicotine given continuously also selectively induces degeneration in fasciculus retroflexus, but in the other half of the tract: the cholinergic axons running from medial habenula in the core of the tract to the interpeduncular nucleus.  

At synapses of medial habenula (MHN) and interpeduncular nucleus (IPN) neurons, application of nicotine increased the frequency of TTX-resistant, spontaneous postsynaptic currents (SSCs) by an average of 5-fold.  

In this study, [ (125)I]-epibatidine was used to label and characterize a novel nAChR subtype found in mouse brain inferior colliculus, interpeduncular nucleus, and olfactory bulb homogenates. The sites with lower agonist affinity comprised 30.0+/-2.2, 58.6+/-0.1 and 48.7+/-3.3% of specific [ (125)I]-epibatidine (200 pM) binding in inferior colliculus, interpeduncular nucleus, and olfactory bulb homogenates, respectively. The profiles were indistinguishable across regions, implying that A85380-resistant [ (125)I]-epibatidine binding sites in inferior colliculus, interpeduncular nucleus, and olfactory bulb represent a single nAChR subtype.  

Several brain regions were richly innervated by ChAT-ir fibers, particularly the telencephalon, optic tectum, thalamus, posterior tubercle, and interpeduncular nucleus.  

Immunoreactivity for rCRMP-4 also was present in certain neurons of the interpeduncular nucleus, median raphe, superior colliculus, and scattered granule cerebellar neurons.  

Very dense staining was observed in the interpeduncular nucleus, the inferior olivary nucleus and the substantia gelatinosa of the spinal cord, whilst dense labelling was observed in the substantia nigra, cochlear nuclei, vestibular nuclei, the spinal nucleus of V, the area postrema and the ventral horn of the spinal cord.  

To study the cholinergic regulation of hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei and interpeduncular nucleus (IPN) we investigated the effects of acute nicotine (0.5 mg/kg, SC, 60 min) on Fos-like immunostaining (IS) during chronic nicotine and its withdrawal in rats.  

The interpeduncular nucleus (IPN) of female rats was studied across the estrous cycle to observe whether the expression of the astroglial marker, glial fibrillary acidic protein (GFAP) reacts to hormonal changes in an area not belonging to the 'endocrine brain'.  

In the brainstem, the red nucleus, substantia nigra, interpeduncular nucleus, cranial motor nuclei (trigeminal motor, abducent, facial, and hypoglossal), sensory cranial nerve nuclei (spinal trigeminal, vestibular, and cochlear), as well as nuclei of the reticular formation, all showed intense immunoreactivity.  

Those include the interpeduncular nucleus and the periventricular nucleus of the hypothalamus.  

In addition, several forebrain regions considered to be part of the limbic system showed pain-induced changes in rCBF, including the anterior dorsal nucleus of the thalamus (23%), cingulate cortex (18%), retrosplenial cortex (30%), habenular complex (53%), interpeduncular nucleus (45%) and the paraventricular nucleus of the hypothalamus (30%).  

However, [ (3)H]naloxone binding was increased in specific regions in NEM-treated sections in the presence of sodium, including bed nucleus of the stria terminalis, interpeduncular nucleus, periaqueductal gray, parabrachial nucleus, locus coeruleus, and commissural nucleus tractus solitarius.  

[ 3H]S15535 binding was highest in hippocampus, frontal cortex, entorhinal cortex, lateral septum, interpeduncular nucleus and dorsal raphe, consistent with specific labelling of 5-HT(1A) receptors.  

nlacZ and lacZ expression persist in the adult brain, in a few ventral domains such as the mammillary bodies of the hypothalamus and the interpeduncular nucleus, potentially derived from the embryonic structures where the Myf5 gene is transcribed.  

Dense mu-stimulated [ 35S]GTPgammaS binding was also found in brainstem nuclei including the interpeduncular nucleus, parabrachial nucleus and nucleus of the solitary tract.  

In 13 rats, lesions of the median raphe, the decussation of the superior cerebellar peduncle, or the interpeduncular nucleus were all ineffective in altering the stimulation frequency required to maintain half-maximal levels of operant responding for stimulation reward.  

Orphanin binding sites were densest in several cortical regions, the anterior olfactory nucleus, lateral septum, ventral forebrain, several hypothalamic nuclei, hippocampal formation, basolateral and medial amygdala, central gray, pontine nuclei, interpeduncular nucleus, substantia nigra, raphe complex, locus coeruleus, vestibular nuclear complex, and the spinal cord.  

Other retrogradely labeled neurons were observed in the taenia tecta, the septum, the nucleus of the lateral olfactory tract, the preoptic area, the lateral hypothalamic area, the mediobasal hypothalamus, the lateral part of the premammillary nucleus, the paraventricular nucleus of the hypothalamus, the paraventricular thalamic nucleus, the central grey, the substantia nigra (SN), the ventral tegmental area (VTA), the lateral nucleus to the interpeduncular nucleus (IIP), the raphe and the locus coeruleus (LC).  

The interpeduncular nucleus of adult male rats was investigated for glial fibrillary acidic protein immunoreactivity. It is concluded that testosterone stimulates the expression of glial fibrillary acidic protein immunoreactivity in the interpeduncular nucleus.  

injection of [ (125)I]IDAM) showed intense labeling in several regions (olfactory tubercle, lateral septal nucleus, hypothalamic and thalamic nuclei, globus pallidus, central gray, superior colliculus, substantia nigra, interpeduncular nucleus, dorsal and median raphes and locus coeruleus), which parallel known SERT density.  

Approximately 52% of the serotonergic neurons in the wallaby brainstem were located in the rostral midline nuclei (caudal linear nucleus, dorsal, median, and pontine raphe nuclei and the interpeduncular nucleus), whereas 21% were found in the caudal midline region (nuclei raphe magnus, obscurus, and pallidus).  

Natriuretic peptide-like immunoreactive fibres were observed in many regions of the brain, being densest in the preoptic/hypothalamic region of the diencephalon and the interpeduncular nucleus of the mesencephalon. Natriuretic peptide-like immunoreactive cell bodies were observed in the dorsal and medial pallium, the medial amygdala, the preoptic nucleus, the ventral hypothalamus, the nucleus posterodorsalis tegmenti mesencephali, and the interpeduncular nucleus.  

MR fibers distribute densely to the following brainstem/forebrain sites: caudal raphe nuclei, laterodorsal tegmental nucleus, dorsal raphe nucleus, interpeduncular nucleus, medial mammillary body, supramammillary nucleus, posterior nucleus and perifornical region of the hypothalamus, midline and intralaminar nuclei of thalamus, dopamine-containing cell region of medial zona incerta, lateral habenula, horizontal and vertical limbs of the diagonal band nuclei, medial septum, and hippocampal formation.  

Quantitative receptor autoradiography reveals the highest levels of BK channel expression in the outer layers of the neocortex, hippocampal perforant path projections, and the interpeduncular nucleus.  

In the interpeduncular nucleus, peptidergic neurons acting as interneurons clearly modulated the afferent input to this nucleus.  

In the brainstem, OFQ was prominent in the ventral tegmental area, substantia nigra, nucleus of the posterior commissure, central gray, nucleus of Darkschewitsch, peripeduncular nucleus, interpeduncular nucleus, tegmental nuclei, locus coeruleus, raphe complex, lateral parabrachial nucleus, inferior olivary complex, vestibular nuclear complex, prepositus hypoglossus, solitary nucleus, nucleus ambiguous, caudal spinal trigeminal nucleus, and reticular formation.  

CYP2D2 was weakly expressed within neurones of the subthalamic nucleus, substantia nigra and interpeduncular nucleus as well as in the hippocampus, dentate gyrus, red nucleus and pontine nucleus. In contrast, CYP2D5 was extensively expressed in the basal ganglia, including neurones in the subthalamic nucleus, substantia nigra and interpeduncular nucleus, as well as other areas of the brain, including the ventral tegmental area, piriform cortex, hippocampus, dentate gyrus, medial habenular nucleus, thalamic nucleus and pontine nucleus.  

The highest GABA(B)R1 labeling was observed in the thalamus, interpeduncular nucleus and medial habenula.  

Autoradiographic mapping of 5-HT1A receptors in SFV-infected brain showed substantially higher binding in nucleus accumbens, tenia tecta, septohippocampal nucleus, septum, medial and basolateral amygdaloid nucleus, anterioventral preoptic nucleus, hippocampus, interpeduncular nucleus, frontal, lateral orbital, and entorhinal cortex and claustrum on days 6 and 14.  

NPY-positive fibers were widely distributed in the brain and locally dense in the ventromedial part of the lateral pallium, in the posterior part of the interpeduncular nucleus, and in the raphe region.  

The highest density of immunoreactive fibres was found in the lateral and medial parabrachial nuclei and in the locus coeruleus; a moderate density was observed in the periaqueductal gray and the central reticular nucleus, and a low density was observed in the interpeduncular nucleus, the nucleus incertus, the raphe pallidus nucleus, the paralemniscal reticular nucleus, the laterodorsal tegmental nucleus, the pericentral division of the dorsal tegmental nucleus and the lateral reticular nucleus. Immunoreactive neurons were observed in the superior central nucleus, the pericentral division of the dorsal tegmental nucleus, the interpeduncular nucleus, the nucleus incertus and the dorsal raphe nucleus.  

Afferent parapineal fibers run in the left fasciculus retroflexus to the interpeduncular nucleus.  

Finally, [ 125I]hPP (Y4/Y5-like) were very discretely distributed in the rat brain, being concentrated in the paraventricular nucleus of the hypothalamus and the interpeduncular nucleus.  

The nuclei composing the central septal division (anterior, lateral, medial, dorsolateral, and ventrolateral nuclei) displayed differential projections to the basal telencephalon, preoptic and anterior hypothalamus, lateral hypothalamic area, dorsal hypothalamus, mammillary complex, dorsomedial anterior thalamus, ventral tegmental area, interpeduncular nucleus, raphe nucleus, torus semicircularis pars laminaris, reptilian A8 nucleus/substantia nigra and central gray.  

Brainstem afferents to the PDVR originate in the dorsal interpeduncular nucleus, the nucleus of the lateral lemniscus and parabrachial nucleus.  

The fasciculus retroflexus (FR) fiber bundle comprises the intense cholinergic projection from the medial division of the habenula nucleus (Hbn) of the epithalamus to the interpeduncular nucleus (IPN) of the limbic midbrain.  

At the level of the interpeduncular nucleus of the mesencephalon, fibres of the ventral bundle bent dorsally to reach the epithalamic area and to continue in the forebrain in a periventricular position.  

Quantitative receptor autoradiography revealed high binding by [ 3H]2-BFI to discrete brain nuclei, notably the area postrema, interpeduncular nucleus, arcuate nucleus, mammillary peduncle, ependyma and pineal gland.  

A few fibers reach the interpeduncular nucleus and the rostral optic tectum.  

Higher CO activity was also found in Lurcher mutants in brain regions directly connected to the cerebellum, such as the lateral vestibular nucleus, the cochlear nucleus, the red nucleus, the ventrolateral thalamus, the dorsal raphe, the interpeduncular nucleus, and the inferior colliculus.  

Opioid binding was heavily concentrated in the caudal nucleus of the solitary tract, nucleus parabrachialis medialis, spinal trigeminal nucleus, inferior olive, and interpeduncular nucleus in all cases analyzed (n = 74).  

In juvenile and adult bats, both neuropeptides are distributed identically throughout the terminal nerve (tn), and they coexist in many parts of the prosencephalon from the olfactory bulb as far caudally as the interpeduncular nucleus.  

Dense [ 3H]PD 128907-labelled sites were observed in the dorsal thalamus, posterior mamilliary nucleus, and dorsomedial interpeduncular nucleus of the rabbit that were not detected in the other species studied.  

The binding was almost exclusively localised to the medial and lateral habenula, interpeduncular nucleus and pineal gland; at 0.1 nM 3[ H]epibatidine it represented about 40% of the total 3[ H]epibatidine binding.  

Following naltrexone administration, mu receptor immunoreactivity was significantly higher in the amygdala, thalamus, hippocampus, and interpeduncular nucleus as compared with the saline-treated control animals. [ 3H]D-Ala2,N-Me-Phe4,Gly-ol5-enkephalin binding to mu opioid receptors was significantly higher in the globus pallidus, amygdala, thalamus, hypothalamus, hippocampus, substantia nigra, ventral tegmental area, central gray, and interpeduncular nucleus of the naltrexone-treated rats.  

Additional neuronal labeling was observed postnatally in the olfactory bulb, cerebral cortex, amygdala, various nuclei of the thalamus, interpeduncular nucleus, linear nucleus of the raphe, pretectal area and superior colliculus.  

Noxious formalin consistently produced detectable, well-localized and typically bilateral increases in rCBF within multiple forebrain structures, as well as the interpeduncular nucleus (Activation Index, AI = 66) and the midbrain periaqueductal gray (AI = 20).  

Among brain regions demonstrating substantial sites less sensitive to cytisine inhibition were the accessory olfactory nucleus, medial habenula, interpeduncular nucleus, fasciculus retroflexus, superior colliculus, inferior colliculus and the pineal gland.  

In the central nervous system, the vesicular acetylcholine transporter terminal fields of the major putative cholinergic pathways in cortex, hippocampus, thalamus, amygdala, olfactory cortex and interpeduncular nucleus were examined and characterized.  

Since the majority of glutamatergic afferents to the median raphe nucleus originates from the lateral habenula and the interpeduncular nucleus, known to connect limbic forebrain to the brainstem, theta associated changes in median raphe nucleus glutamate levels might reflect descending forebrain influences, suggesting therefore a feedback regulation of the hippocampal activity involving brainstem structures..  

Midbrain: IRP-LI was most heavily concentrated in the interpeduncular nucleus, nuclei interfascicularis and rostral-linearis, the subcommissural organ, central gray, and in glia surrounding the cerebral aqueduct.  

At climax stages, immunoreactive fibers and perikarya (weakly stained) were identified in the interpeduncular nucleus and in the dorsal infundibular nucleus.  

In consecutive coronal sections the density of [ 3H]cytisine binding sites was decreased in pre-hypertensive SHR by up to 18% in about 40% of the brain regions examined, with the deficits particularly apparent in frontal cortex (layers 4-6), posterior subiculum, several thalamic regions, and the interpeduncular nucleus.  

The interpeduncular nucleus (IPN) exhibits many complex features, including multiple subnuclei, widespread projections with the forebrain and brainstem, and neurotransmitter heterogeneity.  

The efferents of the habenular nuclei to the interpeduncular nucleus were herein investigated with the retrograde horseradish peroxidase tracing. Injections of cobaltic-lysine complex in the interpeduncular nucleus were also performed. Intensely labeled fibers of the fasciculus retroflexus on the right and left sides of the brain were found to reach the interpeduncular nucleus from the habenular nuclei running prevalently in two routes--one through the medial, and the other through the lateral region of the diencephalon.  

Codistribution that lasted throughout development and into adulthood was noted in a number of brain areas, including the retrosplenial cortex, subiculum, medial habenula, interpeduncular nucleus, locus coeruleus, and brainstem motor nuclei.  

In the limbic system, cadherin-8-positive regions are found in the septal region, habenular nuclei, amygdala, interpeduncular nucleus, raphe nuclei, and hippocampus.  

Autoradiographic localization of [ 3H]cGMP binding sites revealed a heterogeneous distribution with the highest densities in the substantia nigra and interpeduncular nucleus.  

The 5-CT-insensitive binding is located mainly in cortical layer V, caudate-putamen, interpeduncular nucleus and claustrum.  

Previously we demonstrated PP receptors in the brainstem and interpeduncular nucleus, and the PP receptors in the brainstem appear to modulate gastric motility and pancreatic exocrine secretion.  

In the brainstem, they were localized in the superior colliculus, interpeduncular nucleus and some cranial nerve motor nuclei, and further in the ventral horn of the spinal cord.  

Moderate to low somatostatin receptor densities were present in the mesencephalic periaqueductal gray, dorsal raphe, thalamic paraventricular nucleus, interpeduncular nucleus, pineal gland, dorsal tegmental, dorsolateral tegmental and parabrachial nuclei, nucleus of the solitary tract.  

High densities of VAChT-immunoreactive axonal fibers were encountered in areas such as the olfactory bulb, cerebral cortex, striatum, basal forebrain, amygdala, thalamus, hypothalamus including median eminence, hippocampal formation, superior colliculus, interpeduncular nucleus, and pedunculopontine and laterodorsal tegmental nuclei.  

(2) After EA of Tsu-San-Li, the mu receptor binding sites were increased significantly in the following examined structures: the caudate nucleus, septal nucleus, medial preoptic area, amygdalaoid nucleus, periaqueducal gray, interpeduncular nucleus, nucleus raphe magnus, and cervical and lumbar enlargements.  

A low density was found in the superior and inferior colliculi, the interpeduncular nucleus, the nucleus sagulum, the superior central nucleus, the cuneiform nucleus, the accessory dorsal tegmental nucleus, the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and the paralemniscal, magnocellular, gigantocellular, and lateral tegmental fields.  

However, in rat brain sections, [ 125I]Leu31, Pro34-PYY does not appear to bind to the interpeduncular nucleus, a brain region containing a high density of [ 125I]-bPP binding sites.  

Within the olfactory bulb, fibers were found in the internal plexiform, mitral and glomerular cell layers, as well as in the terminal nerve; within the forebrain, fibers were observed in the diagonal band of Broca, rostral and lateral septum, lateral pallium, retrobulbar region pars dorsomedialis, nucleus accumbens, medial preoptic area, hippocampal commissure, amygdala, posterior dorsal ventricular ridge, hypothalamus, median eminence, and the thalamus; within the midbrain, fibers were found in the interpeduncular nucleus and the stratum album periventricular of the optic tectum.  

The highest densities of specific labeling were seen in various cranial nerve nuclei, followed by certain hippocampal sub-fields and laminae, the red nucleus, the interpeduncular nucleus and mid-layers of primary and secondary motor cortices.  

In contrast, specific [ 125I]human pancreatic polypeptide binding sites were detected in this hypothalamic nucleus as well as the medial preoptic area, interpeduncular nucleus, nucleus tractus solitarius, area postrema and dorsal vagal nucleus while cortical areas and the hippocampus contained negligible levels of labeling.  

Some cells of the medial habenula (medioventral part) and of the interpeduncular nucleus (central and lateral parts) were also labelled.  

Especially abundant fiber- and terminal-like patterns were localized to superficial layers of the spinal cord dorsal horn and nucleus caudalis of the spinal tract of the trigeminal, the nucleus of the solitary tract, nucleus ambiguous, locus coeruleus, interpeduncular nucleus, medial aspect of the lateral habenular nucleus, presumed "striasomes" of the caudate-putamen and nucleus accumbens.  

Moderate labeling was detected in layers II-V of most of the cerebral cortex, and in the dorsal lateral geniculate nucleus, substantia nigra (pars compacta and reticularis) and interpeduncular nucleus.  

Experiments included application of the carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) into the habenula, telencephalon, pineal organ, posterior tubercle, and interpeduncular nucleus (IPN).  

FMRFamide fibers were present in the olfactory epithelium, terminal nerve, olfactory bulbs, dorsal and midventral telencephalon, epiphysis, mediolateral thalamus, pretectal gray, optic tectum, infundibulum, posterior interpeduncular nucleus-tegmentum area, and rostral rhombencephalon.  

U50,488H administration resulted in higher numbers of Fos-LI stained neurons compared to morphine in most regions other than the nucleus accumbens and interpeduncular nucleus.  

In agreement with previous binding studies, we observed NK-3 mRNA in the cortex, the amygdala, the hippocampus, the medial habenula, the zona incerta, the paraventricular and supraoptic nuclei of the hypothalamus, the substantia nigra, the ventral tegmental area, the interpeduncular nucleus, the raphe nuclei, the dorsal tegmental nucleus, and the nucleus of the solitary tract.  

Androgen receptor-immunoreactive (AR-ir) cells were observed in the olfactory bulbs, habenula, pineal body, preoptic area, hypothalamus, interpeduncular nucleus, area acusticolateralis, cerebellum, and motor nuclei of the medulla oblongata.  

Ex vivo autoradiography of rat brain after injection of (-)-5-[ 125I]IBVM ((-)-[ 125I]5) clearly delineated small cholinergic-rich areas such as basolateral amygdala, interpeduncular nucleus, and facial nuclei.  

High densities of immunoreactivity were seen within the caudate-putamen, amygdaloid complex, cortical areas, substantia nigra, ventral pallidum, Islands of Calleja, septal nuclei, interpeduncular nucleus, trigeminal motor nucleus and olfactory nuclei.  

Nicotine increased Fos IS significantly in the medial terminal nucleus of accessory optic tract (MT), and tended to increase it in the interpeduncular nucleus (i.p.), as well as in the stress-related areas, the paraventricular hypothalamic nucleus (PVN) and the supraoptic nucleus (SON).  

Intense MOR1-like immunoreactivity (LI) was seen in the 'patch' areas and subcallosal streak in the striatum, medial habenular nucleus, medial terminal nucleus of the accessory optic tract, interpeduncular nucleus, median raphe nucleus, parabrachial nuclei, locus coeruleus, ambiguous nucleus, nucleus of the solitary tract, and laminae I and II of the medullary and spinal dorsal horns. The presynaptic location of MOR1-LI and MOR1/1B-LI was confirmed by lesion experiments: Enucleation, placing a lesion in the medial habenular nucleus, removal of the nodose ganglion, or dorsal rhizotomy resulted in a clear reduction of the immunoreactivities, respectively, in the nuclei of the accessory optic tract, some subnuclei of the interpeduncular nucleus, nucleus of the solitary tract, or laminae I and II of the spinal dorsal horn.  

Using receptor autoradiography it was found: (1) After formalin injection in the rat hind paw, the mu opioid receptor density was significantly increased in certain central areas related to antinociception, i.e., the caudate nucleus, nucleus accumbens, amygdaloid nucleus, periaqueductal gray, interpeduncular nucleus, nucleus raphe magnus and spinal dorsal horn. In comparison with the rats with formalin injection alone, the receptor density in the interpeduncular nucleus, the ventrolateral part of the caudal periaqueductal gray and spinal dorsal horn of the lumbar enlargement was further increased in the rats showing electroacupuncture analgesia.  

A small number of labeled cells was also observed in various areas including the dorsal part of the interpeduncular nucleus, in the midbrain, and the region ventrolateral to the inferior olive, the ventral midline and around the central canal, in the medulla oblongata.  

In the brainstem, strong CYP2D1 immunoreactivity and CYP2D mRNA signal were observed in the substantia nigra compacta, red nucleus, interpeduncular nucleus, pontine grey, locus coeruleus, cerebellum, and the ventral horn of the spinal cord.  

The highest density of immunostaining was found in limbic areas (lateral septum, CA1 area of Ammon's horn and dentate gyrus in the hippocampus, and frontal and entorhinal cortices), in the anterior raphe nuclei, and in the interpeduncular nucleus, in agreement with previous autoradiographic studies with selective radioligands showing the enrichment of these regions in serotonin1A receptor binding sites.  

Highest levels of monoamine oxidase A were measured in the superior cervical ganglion, locus coeruleus, interpeduncular nucleus and ventromedial hypothalamic nucleus.  

Slo immunoreactivity was highly concentrated in terminal areas of prominent fiber tracts: the substantia nigra pars reticulata, globus pallidus, olfactory system, interpeduncular nucleus, hippocampal formation including mossy fibers and perforant path terminals, medial forebrain bundle and pyramidal tract, as well as cerebellar Purkinje cells.  

Here we report the anterograde and retrograde transport of lipophilic fluorescent carbocyanine dye from the interpeduncular nucleus and the habenular nuclei in the fixed goldfish brain. The application of dye into the interpeduncular nucleus resulted in massive labeling of the fasciculus retroflexus and of the habenular neurons.  

The fluorescent carbocyanine dye Dil has been used to retrogradely label the neuronal connections between the forebrain septal area and the interpeduncular nucleus. Previous works based on retrograde horseradish peroxidase transport have identified that only the diagonal band nucleus is a source of the septointerpeduncular projections, but anterograde tracing with labeled amino acids and selective lesions with colchicine have shown that also the posterior septal nuclei project to the interpeduncular nucleus. In the present study, the retrograde labeling in septal nuclei after placing the carbocyanine Dil in the interpeduncular nucleus resulted in the fluorescent labeling of numerous neurons of the diagonal band nucleus.  

Partial lesions were made with kainic acid in the interpeduncular nucleus of the ventral midbrain of the rat. Lesions reduced the extent of immunohistological staining for choline acetyltransferase in the interpeduncular nucleus (p <0.025), but not for tyrosine hydroxylase in the surrounding catecholaminergic A10 region. We conclude that the interpeduncular nucleus mediates nicotinic depression of locomotor activity and dampens nicotinic arousal mechanisms located elsewhere in the brain..  

By midgestation, muscarinic cholinergic receptor binding is already present and regionally distributed, with the highest binding levels in the interpeduncular nucleus, inferior colliculus, griseum pontis, nucleus of the solitary tract, motor cranial nerve nuclei, and reticular formation. Around the time of birth or shortly thereafter, the relative distribution of binding becomes similar to that in the adult, with the highest levels in the interpeduncular nucleus and griseum pontis, although binding levels are higher overall in the infant. In the human interpeduncular nucleus in all age periods examined, muscarinic binding localizes to the lateral portions bilaterally, indicative of a heterogeneous chemoarchitecture.  

Highest increases over control levels (> 250%) were recorded at both ages in interpeduncular nucleus, raphe nuclei and trigeminal nerve tractus.  

Brain regions demonstrating the highest levels of [ 3H]epibatidine binding included the interpeduncular nucleus, medial habenular nucleus, fasciculus retroflexus, superficial gray layer of the superior colliculus and numerous thalamic nuclei, including the anteroventral, dorsal lateral geniculate and gelatinosus nuclei.  

Such were the mitral and tufted cells of the olfactory bulb; anterior olfactory nucleus; neocortical regions; cingulate cortex; retrosplenial cortex; piriform cortex; perirhinal cortex; CA1; CA3; granule cells of the dentate gyrus; superficial layers of the subicular cortex; deep layers of the entorhinal, parasubicular, and presubicular cortices; ventral part of the lateral septal nucleus; septohippocampal nucleus; triangular septal nucleus; nuclei of the diagonal band; bed nucleus of the stria terminalis; ventral pallidum; claustrum; amygdaloid nuclei other than the intercalated nuclei; preoptic region; hypothalamic nuclei other than the medial mammillary nucleus; ventral lateral geniculate nucleus; locus coeruleus; Purkinje cells; many nuclei of the lower brainstem other than the superior colliculus, periaqueductal gray, interpeduncular nucleus, pontine nuclei, and dorsal cochlear nucleus; and dorsal horn of the spinal cord.  

RESULTS: The greatest relative increase of PPE mRNA was seen in lumbar spinal cord (laminae I & II), nucleus raphe magnus, dorsal raphe nucleus, periaqueductal gray, interpeduncular nucleus, preoptic lateral area, amygdala nucleus and caudate-putamen (P < 0.01, vs NS + EA).  

In autoradiography studies, [ 3H]-RS-45041-190 labelled discrete regions of rat brain corresponding to the distribution of I2 subtypes, notably the subfornical organ, arcuate nucleus, interpeduncular nucleus, medial habenular nucleus and lateral mammillary nucleus, and additional sites in the locus coeruleus, dorsal raphe and dorsomedial hypothalamic nucleus.  

Digital image subtractions and region of interest analyses revealed significantly increased fMRI signal intensity in discrete areas of the ventral and dorsal pons, interpeduncular nucleus, basal forebrain, putamen, and cerebellar regions.  

Higher increase was seen in caudate nucleus, accumbens, periaqueductal gray (PAG), interpeduncular nucleus, amygdala (P < 0.01 vs rats treated with electroacupuncture alone); moderate increase was noted in thalamus, lateral area of hypothalamus, spinal dorsal horn (P < 0.01 or 0.05); slight increase appeared in septum, preoptic area, hippocampus, substantia nigra (P < 0.05).  

Bilateral administration of nicotine into the striatum, ventral tegmental area, dorsal hippocampus or the mesopontine tegmentum failed to produce CTA, and administration of nicotine into the interpeduncular nucleus produced CTA in one of two experiments only.  

The highest concentrations were observed in the interpeduncular nucleus and in the hypothalamus (180 and 90 fmol/mg tissue, respectively).  

mu receptor-like immunoreactivity is widely distributed in the rat central nervous system with immunoreactive fibers and/or perikarya in such regions as the neocortex, the striatal patches and subcallosal streak, nucleus accumbens, lateral and medial septum, endopiriform nucleus, globus pallidus and ventral pallidum, amygdala, hippocampus, presubiculum, thalamic and hypothalamic nuclei, superior and inferior colliculi, central grey, substantia nigra, ventral tegmental area, interpeduncular nucleus, medial terminal nucleus of the accessory optic tract, raphe nuclei, nucleus of the solitary tract, spinal trigeminal nucleus, dorsal motor nucleus of vagus, the spinal cord and dorsal root ganglia.  

RESULTS: Ten hours after EA, the expression of PPE mRNA was enhanced; when EA was combined with Dro, the expression of PPE mRNA was further enhanced in many pain-modulation-related nuclei, such as caudate-putamen, accumbens, septal nucleus, diagonal band nucleus, amygdala, hypothalamus, periaqueductal gray (PAG), interpeduncular nucleus, substantia nigra, and the dorsal horn of spinal cord (layer I-II and III-IV).  

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