ChAT-immunoreactive (IR) cells comprise several prominent groups, including the pedunculopontine tegmental nucleus, laterodorsal tegmental nucleus, and parabigeminal nucleus, as well as the cranial nerve somatic motor and parasympathetic nuclei. 
Cholinergic neurons in the parabigeminal nucleus of the rat midbrain were studied in an acute slice preparation. The spontaneous activity of parabigeminal nucleus (PBN) neurons was not due to synaptic input as it persisted in the presence of the pan-ionotropic excitatory neurotransmitter receptor blocker, kynurenic acid, and the cholinergic blockers dihydro-beta-erythroidine (DHbetaE) and atropine.
The majority of cholinergic nuclei typically found in mammals were evident in the microbat, however we could not find evidence for choline-acetyltransferase immunopositive neurons in the Edinger-Westphal nucleus, parabigeminal nucleus, and the medullary tegmental field, as seen in several other mammalian species.
The frog nucleus isthmi (homolog of the mammalian parabigeminal nucleus) is a visually responsive tegmental structure that is reciprocally connected with the ipsilateral optic tectum; cells in nucleus isthmi also project to the contralateral optic tectum.
The parabigeminal nucleus (Pbg) is a subcortical visual center that besides reciprocal connections with the superior colliculus (SC), also projects to the amygdala (Am).
We here present data based on retrograde neuronal labeling following injection of the fluorescent tracer Fluoro-Gold in the rat Am that the parabigeminal nucleus (Pbg) emits a substantial, bilateral projection to the Am.
ALA and SAME treatment diminished the density of GABAergic receptors in the habenular complex and the parabigeminal nucleus of rat brain as studied by immunohistochemical procedures.
In search for other oculomotor-related brainstem structures projecting to PAGdl we studied the projections from the parabigeminal nucleus (PBGN) and its medially adjoining periparabigeminal area (PPBGA).
Autoradiographic labeling of brain slices with radioiodinated UII showed the presence of UII-binding sites in the lateral septum, bed nucleus of the stria terminalis, medial amygdaloid nucleus, anteroventral thalamus, anterior pretectal nucleus, pedunculopontine tegmental nucleus, pontine nuclei, geniculate nuclei, parabigeminal nucleus, dorsal endopiriform nucleus, and cerebellar cortex.
The sSC receives cholinergic projections from the parabigeminal nucleus, and previous studies have revealed the presence of several different nicotinic acetylcholine receptor (nAChR) subunits in the sSC.
However, other regions, such as the substantia nigra (pars compacta), the ventral tegmental area, and the parabigeminal nucleus, receive a dense VGLUT3 terminal labeling although they do not contain VGLUT3 expressing neurons.
The parabigeminal nucleus (PBN) is a small satellite of the superior colliculus located on the edge of the midbrain.
Recent studies have shown that this nucleus and its mammalian homologue, the parabigeminal nucleus, are all visual centers, which receive information from the ipsilateral tectum and project back either ipsilaterally or bilaterally depending on species, but not an auditory center as suggested before.
In contrast to other tetrapods studied with this technique, we failed to find evidence for cholinergic cells in the hypothalamus, the parabigeminal nucleus (or nucleus isthmus), or the cerebral cortex.
Stratum griseum superficiale (SGS) of the superior colliculus receives a dense cholinergic input from the parabigeminal nucleus.
The content of neurons double-labeled for D1/D2 receptors was observed at in differing intensities in the dorsal endopiroform nucleus, the intercalated nucleus of amygdala, the anterior part of the cortical nucleus amygdala, the nucleus of the lateral olfactory tract, the piriform cortex, the parabrachial nucleus, the supraoptic nucleus and the parabigeminal nucleus.
Neurons with both immunoreactivity and in situ hybridization signals of ChAT are observed in the basal forebrain (diagonal band of Broca and nucleus basalis of Meynert), striatum (caudate nucleus, putamen and nucleus accumbens), cerebral cortex, mesopontine tegmental nuclei (pedunculopontine tegmental nucleus, laterodorsal tegmental nucleus and parabigeminal nucleus), cranial motor nuclei and spinal motor neurons.
In particular, we found that the monkey LGN receives a significant cholinergic/nitrergic projection from the pedunculopontine tegmentum, gamma-aminobutyric acid (GABA)ergic projections from the thalamic reticular nucleus and pretectum, and a cholinergic projection from the parabigeminal nucleus.
A few fibers from the ipsilateral retina also directly innervate the SGS, but most of the ipsilateral visual input is provided by cholinergic afferents from the opposing parabigeminal nucleus (PBG). We hypothesize that cholinergic drive from the parabigeminal nucleus may activate presynaptic nicotinic receptors on retinal terminals, thereby facilitating the release of glutamate onto inhibitory neurones.
Immunohistochemical and in situ hybridization studies have revealed the localization of cholinergic neurones in the central nervous system: the medial septal nucleus, the nucleus of the diagonal band of Broca, the basal nucleus of Meynert, the caudate nucleus, the putamen, the nucleus accumbens, the pedunculopontine tegmental nucleus, the laterodorsal tegmental nucleus, the medial habenular nucleus, the parabigeminal nucleus, some cranial nerve nuclei, and the anterior horn of the spinal cord.
Neurons containing hybridization signal for ChAT mRNA were observed in the nucleus of the diagonal band of Broca, the basal nucleus of Meynert, the caudate nucleus, the putamen, the pedunculopontine tegmental nucleus, the laterodorsal tegmental nucleus, the parabigeminal nucleus, the oculomotor nucleus and the trochlear nucleus.
It was also detected in some cell bodies in the reticular part of the substantia nigra, probably the rostral extension of the mesopontine complex, in the parabigeminal nucleus, and around the central canal in the spinal cord but not in cortical, hippocampal, and cerebellar perikarya.
Unilateral, discrete injections of red and green fluorescent latex microspheres or injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) were made into the ferret's superior colliculus (SC) to characterize the topographic organization of the projection from the parabigeminal nucleus (PBN).
Retrograde labeling in auditory structures was rare compared with labeling found in nonauditory structures (e.g., retina, substantia nigra, parabigeminal nucleus).
Here we demonstrate that afferents and targets have interactive roles in the maintenance of cells during development of the mesencephalic parabigeminal nucleus (PB) in rats.
Labeled terminals were observed ipsilaterally in the parabigeminal nucleus, superficial layers of the superior colliculus, dorsal and lateral terminal nuclei of the accessory optic system and pretectal nuclei and contralaterally in the NOT and superficial layers of the superior colliculus.
RESULTS: The reticular nucleus of the thalamus, pedunculopontine nucleus, parabigeminal nucleus, pretectal nucleus of the optic tract, superior colliculus, dorsal raphe nucleus, and tuberomammillary region of the hypothalamus contained many retrogradely labeled neurons ipsilateral to the injections.
The electron microscopic autoradiographic tracing method has been used to examine the morphology and postsynaptic relationships of five projections (retina, cortical area 17, superior colliculus (tectal), parabigeminal nucleus, and pretectum) to the dorsal lateral geniculate nucleus of the greater bush baby Galago crassicaudatus.
A substantial number of retrogradely labelled neurons was also found in the contralateral parabigeminal nucleus. A few retrogradely labelled neurons were found in the ipsilateral and (to a lesser extent) contralateral dorsolateral divisions of the periaqueductal gray matter, as well as in the ipsilateral parabigeminal nucleus and the caudal part of the lateral hypothalamus.
m2, m3 and m5 mRNAs were abundant in the parabigeminal nucleus.
Projection of the presumed primary visual cortical area, superior colliculus and parabigeminal nucleus to the dorsal lateral geniculate nucleus and the lateral posterior--lateral intermedius nuclear complex were described.
In the brainstem, double-labelled neurons were located in the laterodorsal tegmental nucleus, pedunculopontine tegmental nucleus and the parabigeminal nucleus.
Other cholinergic cells and axons, such as the trochlear nerve, the oculomotor nerve and nucleus, and the parabigeminal nucleus, which all label densely for ChAT, stain poorly or not at all for NADPH-diaphorase. It is significant that the parabigeminal nucleus, which provides a cholinergic input to the lateral geniculate nucleus, has no cells that label for NADPH-diaphorase.
The cat superior colliculus (SC) receives a dense cholinergic input from three brainstem nuclei, the pedunculopontine tegmental nucleus, the lateral dorsal tegmental nucleus, and the parabigeminal nucleus (PBG).
The parabigeminal nucleus is cholinergic; however, this nucleus is known to project to the koniocellular layers, along with the non-cholinergic superior colliculus.
The normal ultrastructure of the parabigeminal nucleus and the morphology and synaptic relationships of tectoparabigeminal terminals have been examined. Five different morphological types of terminals have been observed within the parabigeminal nucleus.
These areas include the medial preoptic area of the hypothalamus, the nucleus accumbens, the lateral septum, several regions of the dorsal pontine tegmentum (central gray, dorsal raphe, locus coeruleus, pedunculopontine and laterodorsal tegmental nuclei, parabrachial nuclei) and an area medial to the parabigeminal nucleus at the ponto-mesencephalic junction.
Neurons in the pedunculopontine and laterodorsal tegmental nuclei evinced moderate hybridization signal, whereas cells of the parabigeminal nucleus were very weakly reactive.
A projection from the parabigeminal nucleus (Pbg) to the striate-recipient zone of the pulvinar nucleus in the prosimian Galago was identified by anterograde and retrograde transport methods.
High densities of receptor-associated silver grains were found in the olfactory bulb (internal plexiform layer), neocortex (layer III), nucleus accumbens, parasubiculum, subbrachial nucleus, parabigeminal nucleus, dorsal vagal complex, area postrema and the A2 region.
Neurons in the pedunculopontine and laterodorsal tegmental nuclei were moderately reactive, whereas cells of the parabigeminal nucleus exhibited a very weak hybridization signal.
A high density of ChAT-positive terminals was found in all or parts of these structures: interpeduncular nucleus, superficial grey layer of the superior colliculus (ferret), intermediate layers of the superior colliculus, lateral part of the central grey (rat), an area medial to the parabigeminal nucleus (rat), pontine nuclei, ventral tegmental nucleus (rat), midline pontine reticular formation, and an area ventral to the exit point of the 5th nerve (ferret). A medium density of ChAT-positive terminals was observed in all or parts of: the substantia nigra zona compacta (ferret), ventral tegmental area (ferret), superficial grey layer of the superior colliculus, intermediate and deep layers of the superior colliculus, lateral central grey, area medial to the parabigeminal nucleus, inferior colliculus, dorsal tegmental nucleus, ventral tegmental nucleus (ferret), pontine nuclei, ventral nucleus of the lateral lemniscus (ferret), midline pontine reticular formation, ventral cochlear nucleus, dorsal cochlear nucleus, lateral superior olive, spinal trigeminal nuclei, prepositus hypoglossal nucleus, lateral reticular nucleus, paragigantocellular nucleus, and the dorsal column nuclei including the cuneate, external cuneate, and gracile nuclei.
A protracted maturation of both AChE staining and ChAT immunoreactivity also was observed in the sources of cholinergic afferents to the superior colliculus, which include the parabigeminal nucleus, and the pedunculopontine (PPN) and lateral dorsal tegmental (LDTN) nuclei. At 21 dpn, however, ChAT immunoreactivity virtually disappeared in the parabigeminal nucleus and significantly decreased in PPN and LDTN. At 35 dpn, AChE staining showed a significant, though temporary (4 weeks), decrease in the parabigeminal nucleus, but not in the PPN and LDTN, that subsequently increased to the adult level of staining at 70 dpn. Injections of HRP into the superior colliculus retrogradely labeled many neurons in the parabigeminal nucleus, but few, if any, neurons in the PPN or LDTN at 1 dpn.
In contrast, the estimated number of ChAT-immunoreactive cell bodies in cranial nerves III and IV, in the mesencephalic reticular formation, and in the parabigeminal nucleus was not different from that of controls.
We examined the distribution of labeled neurons in the parabigeminal nucleus of the monkey following injections of retrograde fluorescent tracers into the superior colliculus. The results suggest a rough topographic organization of the parabigeminal nucleus, with the lower quadrant represented anteriorly and the upper quadrant posteriorly. We also found bilateral projections from the parabigeminal nucleus to both superior colliculi, but the crossed projection appeared to terminate only in that part of the colliculus where the vertical meridian is represented.
This surviving tectal AChE thus is probably presynaptic and could be contained at least partly in cholinergic afferents from the parabigeminal nucleus and pontomesencephalic tegmentum. The collicular lesions had no obvious effect on AChE staining in the parabigeminal nucleus or in the C-laminae or ventral division of the lateral geniculate nucleus..
This contingent of fibres travels more rostrally above the cerebral peduncle, distributing terminals to the substantia nigra, ventral tegmental area and parabigeminal nucleus before fanning out and turning rostrally to contribute terminals to ventral thalamus, subthalamus and zona incerta, then continuing on to supply amygdala, substantia innominata, lateral preoptic nucleus, the diagonal band of Broca and the lateral septal nucleus.
Described here is an aberrant parabigeminothalamic projection that follows neonatal lesions of the superior colliculus in rats, with evidence that this anomalous projection may sustain a normal number of neurons in the parabigeminal nucleus after early removal of the latter's tectal target. The aberrant projection was traced radioautographically to the tectorecipient zone of the lateral posterior nucleus after an injection of tritiated amino acid in the parabigeminal nucleus. Ablation of the superior colliculus at birth failed to produce a net cell loss in the contralateral middle division of the parabigeminal nucleus after the period of natural neuronal death. Lesions extending toward the anomalous terminal field in the lateral posterior nucleus, however, prevented the survival of a normal number of neurons in the parabigeminal nucleus. We conclude that the anomalous target in the tectorecipient zone of the lateral posterior nucleus effectively replaces the normal projection field in the superior colliculus, with regard to the trophic requirements for neuronal survival during development of the parabigeminal nucleus..
This study was designed to test the effects of simultaneous deafferentation and target removal on cell death in the parabigeminal nucleus.
From these areas, fragment C exhibited retrograde transneuronal transport, strongly and reliably labeling regions that project to retinorecipient areas, including layers V and VI of visual cortex, the parabigeminal nucleus, the suprageniculate nucleus, and the reticular thalamus.
In both of these species, very dense SP-like immunoreactivity (SPLI) was also visible in the parabigeminal nucleus. Combination of retrograde tracing with True blue or Fluorogold and immunocytochemistry demonstrated that SP-positive SC neurons projected to the parabigeminal nucleus in both hamster and rat. Destruction of the superficial layers of the SC resulted in a virtually complete loss of SPLI in the ipsilateral parabigeminal nucleus in both species.
Double-label experiments show that cholinergic projections to the GL originate from two sources, the pedunculopontine reticular formation (PPT) and the parabigeminal nucleus (Pbg).
Neurons containing both labels were found in the parabigeminal nucleus, and in the lateral dorsal and pedunculopontine tegmental nuclei of the pontomesencephalic reticular formation. The similarities between the laminar distributions of the ChAT terminals and the terminations of the pathway from the parabigeminal nucleus (Graybiel: Brain Res.
After unilateral destruction of the parabigeminal nucleus, the ChAT immunoreactivity was markedly reduced in the rostral aspect of the contralateral SGS, and moderately in the caudal aspect of the ipsilateral SGS..
The number of neurons and glia in the albino mouse parabigeminal nucleus remains constant between 6 and 31 months of age. The presence of a small number of mitotic and pyknotic cells in the parabigeminal nucleus indicates a slow turnover of the glial population throughout life. The stability of the neuron number in the parabigeminal nucleus may be due to the reciprocal innervation of neurons of the superior colliculi and parabigeminal nuclei protecting each other from transneuronal degeneration which might otherwise occur as a consequence of loss of retinal ganglion cells. Alternatively, since each neuron in the parabigeminal nucleus probably synapses with many tectal neurons, the loss of only some of its target neurons would probably not lead to transneuronal degeneration..
Neurons were antidromically activated from stimulating electrodes implanted in the ipsilateral medial longitudinal fasciculus (n = 24), the ipsilateral interstitial nucleus of Cajal (n = 6), the ipsilateral parabigeminal nucleus (n = 2), the contralateral superior colliculus (n = 6) and the contralateral cerebellar posterior peduncle (n = 24).
Following a unilateral injection of a tracer into the superficial superior colliculus, retrogradely labelled choline acetyltransferase-immunoreactive neurons were found in the dorsal and ventral subnuclei of the ipsilateral parabigeminal nucleus. The data from the double labelling experiments indicate that the choline acetyltransferase-immunoreactive terminals observed in the superficial layers represent the terminal field of an ipsilateral cholinergic projection from the parabigeminal nucleus.
In contrast, in the brains of guinea pigs processed by identical technical parameters, transneuronal anterograde labeling was readily recognized in the contralateral striate cortex, thalamic reticular nucleus, and parabigeminal nucleus.
In addition, the contralateral parabigeminal nucleus provided a major input to the rostral part of the anterior pretectal nucleus.
Partial deafferentation of the middle division of the parabigeminal nucleus (PBm) was produced before the period of naturally occurring cell death, by reducing the neuronal population of the superior colliculus following partial lesions or eye removal.
Radioactive materials were found in the pulvinar nucleus(Pul), parabigeminal nucleus(PB) and dorsal lateral pontine gray(DLP).
Two (possibly three) groups of AChE-carrying fibers can be traced from the optic chiasm to their apparent sites of termination (or origin) in the parabigeminal nucleus, ventral lateral geniculate nucleus, and dorsal LGN.
With colchicine treatment, calcitonin gene-related peptide-like immunoreactive cells were found in more areas of the brain stem such as the abducens nucleus, parabigeminal nucleus, principal oculomotor nucleus, trochlear nucleus and central gray, along with the nuclei which had shown calcitonin gene-related peptide immunoreactivity in the untreated animals.
The distribution of neurons and fibres that contain substance P, cholecystokinin-8, vasoactive intestinal polypeptide, corticotropin-releasing factor, calcitonin-gene-related peptide, choline acetyltransferase, tyrosine hydroxylase, somatostatin, leucine-enkephalin, and neuropeptide Y was examined in the parabigeminal nucleus of the rat by immunohistochemistry. Many choline acetyltransferase-like immunoreactive or calcitonin-gene-related peptide-like immunoreactive neurons were observed in the dorsal, middle and ventral subdivisions of the parabigeminal nucleus. Fibres containing cholecystokinin-8, substance P or vasoactive intestinal polypeptide were abundant in the parabigeminal nucleus. Tyrosine hydroxylase-like immunoreactive fibres were scattered in the parabigeminal nucleus..
Two sources for the ChAT-immunoreactive fibers in the GL have been identified--the parabigeminal nucleus (Pbg) and the pedunculopontine tegmental nucleus (PPT)--and the contribution that each makes to the distribution of ChAT-immunoreactive fibers in GL was determined by combining immunocytochemical, axonal transport, and lesion methods.
Patches of terminal labeling were located ipsilaterally in the lateral mesencephalic reticular formation near the parabigeminal nucleus and the ventrolateral pontine reticular formation.
Injections of WGA-HRP into the superior colliculus gave terminal label in the cuneiform nucleus and also in surrounding structures which included central grey, the midbrain tegmentum bordering the parabigeminal nucleus, and the external nucleus of the inferior colliculus.
Cells in the parabigeminal nucleus are also labelled but these cells contain low levels of cholinesterase.
They were reciprocally connected with the dorsal and ventral lateral geniculate nuclei, the pretectum, nucleus lateralis posterior (LP), the parabigeminal nucleus and the contralateral SC.
Natural and induced cell degeneration were studied in the mesencephalic parabigeminal nucleus of postnatally developing rats. Natural cell death in the normal parabigeminal nucleus had already started at birth, was maximal at 3 days, and proceeded with a declining rate until postnatal days 8-10 in the dorsal, middle, and ventral divisions that compose the nucleus. The frequency curves of degenerating cells were poor predictors of the absolute changes in neuron numbers, and evidence was found of continued postnatal migration of neurons into the developing parabigeminal nucleus..
We compared the laminar location and morphology of superior colliculus cells projecting to the dorsal and ventral lateral geniculate nuclei (LGd, LGv), the pretectum (PT), the parabigeminal nucleus (Pb), and nucleus lateralis posterior (LP) in the ground squirrel Spermophilus tridecemlineatus.
Other groups of ChAT+ cells were identified within the periolivary nuclei, parabigeminal nucleus, prepositus hypoglossi nucleus, and the medial and inferior vestibular nuclei.
Additional positive neurons were seen in the parabigeminal nucleus and in the dorsal periaqueductal gray in kitten material.
Essentially, six regions in the brainstem contained retrogradely labeled cells: the superior colliculus, the parabigeminal nucleus, the dorsal raphe nuclei, the parabrachial area of the central tegmental field, the marginal nucleus of the brachium conjunctivum, and the nucleus coeruleus.
Essentially all of the cells in the parabigeminal nucleus were found to be ChAT-positive.
Cell bodies staining positively for choline acetyltransferase are found in a satellite of the superior colliculus, the parabigeminal nucleus..
The contralateral efferent connections of rat parabigeminal nucleus (pbgn) were studied by means of retrograde transport of horseradish peroxidase (HRP) after focal HRP injection into the superior colliculus (SC), the optic tract, the dorsal part of the lateral geniculate nucleus (LGNd) and the lateroposterior nucleus of the thalamus (LP).
The following areas were newly identified as areas rich in CHAT-I fibers: the interpeduncular nucleus, medial geniculate body, central gray matter of pons, pontine nucleus, parabigeminal nucleus, dorsal tegmental nucleus of Gudden, lateral trapezoid nucleus, inferior colliculus, dorsal and ventral cochlear nuclei, medial and lateral vestibular nuclei, reticular formation of medulla oblongata, and gelatinosa of caudal trigeminal spinal tract nucleus.
Terminal fields associated with the major bundle of fibres are found in an area medial to the brachium of the inferior colliculus; the parabigeminal nucleus and adjacent tegmentum; the ventrolateral midbrain reticular formation; and the lateral pontine nuclei.
At midbrain, pontine and medullary levels, additional labelled regions were: the substantia nigra, cuneiform nucleus, parabigeminal nucleus, raphe magnus, and reticular areas.
CNS regions where there was a substantial density of binding sites for iodinated substance P and few or no sites for iodinated eledoisin, neuromedin K, and substance K included cortical layers I and II, olfactory tubercle, nucleus accumbens, caudate-putamen, globus pallidus, medial and lateral septum, endopiriform nucleus, rostral thalamus, medial and lateral preoptic nuclei, arcuate nucleus, dorsal raphe nucleus, dorsal parabrachial nucleus, parabigeminal nucleus, cerebellum, inferior olive, nucleus ambiguus, retrofacial and reticular nuclei, and spinal cord autonomic and somatic motor nuclei.
DYN B cell bodies were present in nonpyramidal cells of neo- and allocortices, medium-sized cells of the caudate-putamen, nucleus accumbens, lateral part of the central nucleus of the amygdala, bed nucleus of the stria terminalis, preoptic area, and in sectors of nearly every hypothalamic nucleus and area, medial pretectal area, and nucleus of the optic tract, periaqueductal gray, raphe nuclei, cuneiform nucleus, sagulum, retrorubral nucleus, peripeduncular nucleus, lateral terminal nucleus, pedunculopontine nucleus, mesencephalic trigeminal nucleus, parabigeminal nucleus, dorsal nucleus of the lateral lemniscus, lateral superior olivary nucleus, superior paraolivary nucleus, medial superior olivary nucleus, ventral nucleus of the trapezoid body, lateral dorsal tegmental nucleus, accessory trigeminal nucleus, solitary nucleus, nucleus ambiguus, paratrigeminal nucleus, area postrema, lateral reticular nucleus, and ventrolateral region of the reticular formation.
The parabigeminal nucleus receives its major input from the superficial layers of the superior colliculus via the tectoparabigeminal projection. This close connectional association between the superficial gray and the parabigeminal nucleus is reflected in the collicularlike response characteristics of parabigeminal neurons (see Sherk: Brain Res. Further documentation of the connectional relationship between the superior colliculus and the parabigeminal nucleus comes from the present data. Thus, our retrograde and anterograde transport findings reveal an extensive projection from the parabigeminal nucleus to layers 3 and 6 and several interlaminar zones of the contralateral dorsal lateral geniculate nucleus.
A method for the concurrent visualization of ChAT and transported horseradish peroxidase showed that a major extrinsic source for this cholinergic input is in the parabigeminal nucleus.
Our connectional findings reveal that axons arising from the superior colliculus and the parabigeminal nucleus influence the W-cell system via their innervation of the two small-celled geniculate laminae (internal and external koniocellular) and the interlaminar zones; parabigeminal axons also innervate each of the 4 non-tectally innervated layers.
The general topographical patterns of some of the afferent and efferent projections were also determined: the caudal and rostral parts of the parabigeminal nucleus project to the caudal and rostral regions, respectively, of the superior colliculus; caudal superior colliculus projects to the most lateral, and lateral superior colliculus to the most caudal part of the terminal field in the dorsal lateral geniculate nucleus; caudolateral superior colliculus projects to the caudal ventrolateral part of the ventral lateral geniculate nucleus, while rostromedial parts of the colliculus project more rostrally and dorsomedially.
Quantitative morphological changes in the superior colliculus (SC) and the parabigeminal nucleus (PB) were studied in hereditary bilaterally microphthalmic rat, which lacks the optic nerve completely.
Experiments conducted after large HRP deposits invading almost all the collicular layers resulted in the labeling of visual centers (cortical areas 17, 18 and 18a, ventral lateral geniculate nucleus, nucleus of the posterior commissure, nucleus of the optic tract, anterior and olivary pretectal nuclei, parabigeminal nucleus); somatosensory centers (cortical area SmI, principal and spinal tract trigeminal nuclei) auditory centers (auditory cortex, inferior colliculus and nuclei of the lateral lemniscus) and various other centers (zona incerta, substantia nigra, cingulate and motor cortices, and some hypothalamic, thalamic, pontine reticular and deep cerebellar nuclei). Deposits limited to the deep SC layers resulted in the labeling of a smaller number of structures: visual centers (cortical area 18a, nucleus of the posterior commissure, parabigeminal nucleus); somatosensory centers (cortical area SmI, principal and spinal tract trigeminal nuclei); auditory centers (inferior colliculus, nuclei of the lateral lemniscus); and various other centers (zona incerta, substantia nigra, cingulate cortex, some hypothalamic nuclei, posterior thalamic nucleus, central gray, cuneiformis and subcuneiformis nuclei, pontine reticular nucleus pars oralis).
The lateral reticular region has strong projections to the lateral geniculate body and together with the parabigeminal nucleus forms the midbrain visual complex..
These included the parabigeminal nucleus, paralemniscal zone, dorsolateral pons, and inferior olive.
The lateral mesencephalic tegmentum close to the parabigeminal nucleus.
Labelled cells were identified in a variety of structures, including the nucleus of the optic tract (NOT), the posterior pretectal nucleus (NPP), the superior colliculus (SC), the parabigeminal nucleus (PBN), the midbrain reticular formation (MRF), locus coeruleus and nucleus sub-coeruleus, the substantia nigra (SN), and parts of the raphe complex.
Evidence was obtained for a crossed collicular projection to the rat parabigeminal nucleus (Pbg) in addition to the established uncrossed one.
In the cases injected with WGA and having a survival time of at least two days cells were labeled in the lateral mesencephalic tegmentum, ventral to the parabigeminal nucleus and in the periaqueductal gray.
The retino-recipient layers of the superior colliculus project predominantly to the dorsal and ventral divisions of the ipsilateral parabigeminal nucleus, while receiving an input chiefly from the medial division of the contralateral nucleus. A variety of retrograde tracing techniques was used to confirm that there is a projection from the medial division of the parabigeminal nucleus to the contralateral dorsal lateral geniculate nucleus in normal adult hooded rats.
The parabigeminal nucleus also contained a few labelled cells.
After injections placed dorsal to the stratum opticum in the superior colliculus, the parabigeminal nucleus is the only mesencephalic and/or rhombencephalic structure in which labeled neurons are observed. The number of labeled neurons in the parabigeminal nucleus increases after injections that include both the superficial and the deep layers of the superior colliculus. The posterior third of the parabigeminal nucleus sends scant efferents to wide areas of the ipsilateral and contralateral colliculi, and a dense projection to the medial and intermediate, medial and caudal and central and intermediate parts of the ipsilateral colliculus. There are also consistent projections from the posterior third of the parabigeminal nucleus to the central and rostral and medial and rostral parts of this ipsilateral colliculus.
Degenerative effects in the parabigeminal nucleus were studied in adult rats that had received lesions of the superior colliculus at different postnatal ages. Unilateral lesions lead to complete degeneration of the dorsal and ventral divisions of the parabigeminal nucleus, which connect reciprocally with the damaged tectum, and produce effects on the middle division which receives afferents from the ipsilateral and projects to the contralateral tectum.
Projections of the parabigeminal nucleus to the contralateral superior colliculus and dorsal lateral geniculate nucleus were examined in normal adult pigmented rats and in adult rats from which one or both eyes had been removed at birth. The corresponding termination patterns of the contralateral parabigeminal nucleus and the ipsilateral retina in the normal superior colliculus may indicate a functional and/or developmental interdependence between the projections from these two regions. The even greater expansion of the projection from the parabigeminal nucleus to the colliculus which receives an expanded projection from the ipsilateral retina of unilaterally enucleated rats suggests that the functional organization of the ipsilateral retinotectal projection may be capable of restricting the size of the terminal field of the crossed parabigeminotectal projection..
Contralateral labelling appeared in the ventral LGB and parabigeminal nucleus.
Anatomical techniques are used to demonstrate a projection from the parabigeminal nucleus (PBG) to the contralateral dorsal lateral geniculate nucleus (dLGN) in adult pigmented rats which had been bilaterally enucleated at birth.
Other areas which commonly projected into the transplants included pretectum, parabigeminal nucleus, superior colliculus, and the brachial region of the inferior colliculus.
In the nucleus of Darkschewitsch peak production time was on day E12 and 13, extending to day E15; in the Edinger-Westphal nucleus the time span was the same but with a pronounced between days E13; finally, the neurons of the parabigeminal nucleus were produced between days E13 and E15 with a peak on day E14.
Radioisotope injections restricted to the superficial layers reveal dense projections to the parabigeminal nucleus, the pretectum, the inferior and lateral pulvinar nuclei, and to the ventral and dorsal lateral geniculate nuclei.
Neurons projecting to this nucleus were also present in the intermediate layers of the superior colliculus, lateral hypothalamus and parabigeminal nucleus.
Iontophoretic deposit of the marker was used in most animals, and consistent projections from the hypothalamic ventromedial nucleus, the lateral part of the substantia nigra and the parabigeminal nucleus (NPB) were observed.
The aim of these experiments was to analyze the organization of the reciprocal connections between the cat's superior colliculus and parabigeminal nucleus. A population of cells in the superficial gray and upper optic layers of the colliculus was labeled retrogradely by horseradish peroxidase injections into the parabigeminal nucleus. A map of the visual field within the parabigeminal nucleus was reconstructed by plotting visual receptive fields at 350 parabigeminal sites with microelectrodes.
The visual-response properties of single cells in the cat's superior colliculus and parabigeminal nucleus were compared. In the colliculus, 151 cells (restricted to the upper layer) were studied, and in the parabigeminal nucleus, 134 cells. Spontaneous activity was much higher in the parabigeminal nucleus than in the colliculus. These data suggest that a physiologically distinct population of tectal cells sends input to the parabigeminal nucleus, probably with some convergence on individual cells..
The parabigeminal nucleus of the rat was made up of the dorsal, middle and ventral subgroups.
Visual structures: ventral lateral geniculate nucleus, parabigeminal nucleus, pretectal area (nucleus of the optic tract, posterior pretectal nucleus, nuclei of the posterior commissure). Evidence is presented that only the parabigeminal nucleus, the nucleus of the optic tract, and the posterior pretectal nucleus project to the superficial collicular layers (striatum griseum superficiale and stratum opticum), while all other afferents terminate in the deeper layers of the colliculus.
Afferent and efferent connections of the parabigeminal nucleus (PBG) of the cat have been demonstrated by means of horseradish peroxidase (HRP) tracing technique.
The connections between the nucleus isthmi and the tectum in the frog are strinkingly similar to the connections between the parabigeminal nucleus and the superior colliculus of mammals..
After deep collicular injections numerous labeled cells were consistently found in the parabigeminal nucleus, the mesencephalic reticular formation, substantia nigra pars reticulata, the nucleus of posterior commissure, the pretectal area, zona incerta, and the ventral nucleus of the lateral geniculate body. Only the parabigeminal nucleus and the pretectal area showed labeled cells following injections in the superficial layers of the superior colliculus.
The ipsilateral pathway courses laterally and ventrocaudally to terminate within the parabigeminal nucleus, the mesencephalic reticular formation, the dorsal lateral pontine gray (in several discrete patches), the dorsal lateral wing of the nucleus reticularis tegmenti pontis, and within the nucleus reticularis pontis oralis.
Following lesions of the deep layers of the superior colliculus, degenerated axonal endings were found in the central gray, magnocellular medial geniculate nucleus, suprageniculate nucleus, limitans nucleus, lateral posterior nucleus, medial and oral pulvinar, nucleus of the accessory optic tract, zona incerta, subdivisions of the ventral lateral and ventral posterior lateral nuclei, ventral posterior inferior nucleus, denosocellular and multiform dorsomedial nuclei, all intralaminar nuclei, inferior colliculus, parabigeminal nucleus, olivary nucleus, reunions nucleus, Forel's Field H and an undefined midbrain nucleus.
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