Pontine Gray

The precerebellar neurons (PCNs), generated in the lower rhombic lip (LRL), migrate towards their destinations: some neurons form the pontine gray nucleus (PGN) and reticulotegmental nucleus (RTN) in the ipsilateral pons, while others form the lateral reticular and external cuneate nuclei in the contralateral medulla after crossing the midline.  

Furthermore, there were projections into the reticular formation of the lateral and dorsocaudal medulla and lateral pons, into nucleus gracilis, inferior and medial vestibular nuclei, lateral reticular nucleus, ventral raphe, pontine gray, superior colliculus, PAG and mediodorsal thalamic nucleus.  

In addition, strong hybridization signals were localized in various nuclei: main and accessory olfactory bulb, compact part of the substantia nigra, pontine gray matter, tegmental reticular nucleus, Edinger-Westphal nucleus, trigeminal motor nucleus, locus coeruleus, mesencephalic trigeminal nucleus, raphe nuclei, facial nucleus, ambiguus nucleus, dorsal motor vagal nucleus, and inferior olivary nucleus.  

Using Fluoro-Jade staining to detect degenerating neurons, we have identified three new brain regions that show neuronal cell necrosis as a result of exposure to L-CPA, these are the medial habenular nucleus, pontine gray and inferior olivary nucleus. The neuronal cell necrosis at these new sites was both time and dose dependent; young 22-day-old rats, which are refractory to L-CPA-induced cerebellar granule cell necrosis, did however show some neuronal cell degeneration in the medial habenular, pontine gray and inferior olivary nuclei. Treatment of rats with MK-801 30 min prior to L-CPA, afforded complete protection against the neuronal cell injury in the medial habenular, pontine gray and inferior olivary nuclei, similar to that previously reported for the cerebellum, supporting an excitotoxic mechanism of neuronal cell death. The basis for the neuronal cell loss in the medial habenular nucleus, pontine gray and inferior olivary nucleus, in addition to the major site in the cerebellum, and the sensitivity of particular cerebellar lobes is not currently understood.  

In contrast, injections made by other investigators into cortical areas anterior to the central sulcus revealed cerebrocortical afferents to NRTP, in addition to nuclei of the basal pontine gray. The combined anterograde and retrograde labeling data indicated that visuo-motor cortico-pontine pathways arising from parietal cortices target only the basal pontine gray, whereas the NRTP, together with select pontine nuclei, is a recipient of afferents from frontal cortical areas.  

The resulting mice developed brain tumors that originated in the pontine gray, just rostral to the fourth ventricle.  

In 33 animals, the distributions of afferents (visual from extrastriate cortex; somatic from the primary somatosensory cortex, the trigeminal nucleus and the cervical spinal cord) and efferents (cells of origin of the crossed descending bulbospinal tract and uncrossed pathway to the pontine gray, the ascending system to the medial dorsal thalamus) were examined in a tangential plane following applications of horseradish peroxidase-wheatgerm agglutinin conjugate (used as an anterograde and retrograde tracer).  

The resulting mice, and offspring from four individual lines, developed brain tumors that originated in the pontine gray, just rostral to the fourth ventricle.  

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.  

Staining was also observed in the gracile nucleus, the mesencephalic trigeminal nucleus, and the central pontine gray.  

Immunoreactive fibres were observed in the following; the inferior central nucleus; the pontine gray nuclei; the Kölliker-Fuse nucleus; the motor trigeminal nucleus, the anteroventral cochlear nucleus; the abducens nucleus; the retrofacial nucleus; the superior, lateral, inferior, and medial vestibular nuclei; the lateral nucleus of the superior olive; the external cuneate nucleus; the nucleus of the trapezoid body; the postpyramidal nucleus of the raphe; the medial accessory inferior olive; the dorsal accessory nucleus of the inferior olive; the nucleus ambiguus; the principal nucleus of the inferior olive; the preolivary nucleus; the nucleus ruber; the substantia nigra; and in the area postrema.  

Sparse dopamine-immunoreactive fibers were observed in the pontine gray, motor trigeminal nucleus, inferior olive and major axon bundles such as the dorsal and ventral tegmental bundles, where numerous noradrenergic fibers have been reported.  

Hypothalamopontine fibers extended caudally through the pontine tegmentum dorsal to the nucleus reticularis tegmenti pontis and then coursed ventrally from the main descending bundle toward the ipsilateral basilar pontine gray. Some hypothalamopontine fibers crossed the midline in the tegmental area just dorsal to the pontine gray to terminate in the contralateral BPN.  

Symmetrical staining was observed in the autonomic, tegmentum pontine, pontine gray, locus coeruleus and other reticular-related nuclei. However, some brainstem structures including the ipsilateral inferior VN and the bilateral pontine gray nuclei displayed a second peak of Fos expression (24 h-1 week).  

The brunt of the changes, however, are borne by the pontine gray, the arcuate nucleus, the pontobulbar body, and the paramedian reticular nucleus.  

Additionally, normal fascicles did not have their own nutritional arteries, and were nourished by arterioles and capillaries from the surrounding pontine gray matter.  

Because it is known that this cortex gives rise to axons ending in the spinal cord, facial nucleus, pontine gray, red nucleus, putamen, and primary and supplementary motor cortices, we suggest that the cingulate motor cortex forms a strategic cortical entry point for limbic influence on the voluntary motor system..  

Brainstem abnormalities were characterized by abnormal curvature, caudal displacement of the pontine gray nuclei which were located caudally along the ventral border of the superior olivary complex, a drastic decrease in Purkinje cell axons in all the vestibular nuclei and the presence of dystrophic processes in at least two calbindin-positive cell groups of the dorsal pontine region.  

In situ hybridization revealed prominent mGluR8 mRNA expression in olfactory bulb, pontine gray, lateral reticular nucleus of the thalamus, and piriform cortex.  

Descending projections follow two pathways that also converge at various levels: a dorsal pathway in the midbrain periventricular system travels through, and primarily innervates, the periaqueductal and pontine gray, and a ventral pathway extends through ventromedial regions of the brainstem.  

Most incertopontine axons descend to the basilar pons in association with fibers of the medial lemniscus or crus cerebri and reach ipsilateral ventral and medial pontine gray regions. A sparse number of terminals are evident in the contralateral medial pontine gray. Dual orthograde labeling experiments indicate that some pretectal terminal fields in the pontine gray are shared with incertopontine projections and with afferents from the dorsal column nuclei.  

Basal levels of CRF-R transcripts were observed in several defined regions of the brain, such as the medial septal nucleus, nucleus of the diagonal band, basolateral and medial nuclei of the amygdala, red nucleus, pontine gray, and various layers of the cerebral cortex.  

Strong basal levels of CRF-R transcripts were observed in several regions of the brain (piriform cortex, medial and basolateral nuclei of the amygdala, red nucleus, pontine gray, cerebellum, laterodorsal tegmental nucleus, caudal division of the zona incerta, nucleus incertus, spinal and principal sensory nuclei of the trigeminal nerve, and various layers of the cortex).  

They penetrated the basal pontine gray matter as longitudinal pontine fibers and entered the medullary pyramid. Both in normal and reeler mice, collaterals arising from these CS fibers projected to the ipsilateral red nucleus, basal pontine gray matter, inferior olivary complex, and the contralateral gracile nucleus.  

The densest clusters of immunoreactive perikarya were found in the inferior and superior colliculi, the inferior olive, the periaqueductal gray, the central tegmental field and the substantia nigra, whereas the central linear nucleus, the locus coeruleus, the nucleus incertus, the dorsal and ventral nuclei of the lateral lemniscus, the cuneiform nucleus, the pontine gray, the Kölliker-Fuse nucleus, the dorsal motor nucleus of the vagus and the medial nucleus of the solitary tract had the lowest density.  

Extrathalamic regions receiving input included the pontine gray, external nucleus of the inferior colliculus, pericollicular tegmentum, nucleus of the brachium of the inferior colliculus, and pretectum.  

Successful HRP injections were made into the predorsal bundle (PB), the tecto-pontine-bulbar pathway (TPB) and the cuneiform region (CFR), the inferior olive (IO), the dorsolateral pontine gray nucleus (PGD), and the pedunculopontine tegmental nucleus (PPTN).  

The densely innervated reticular regions in the DCN of cats and the corresponding regions in monkeys are predominantly involved in the processing of sensory information to the cerebellum, either directly, or indirectly through projections to the inferior olive, pontine gray, tectum, pretectum, red nucleus, or zona incerta.  

Finally, a few immunoreactive fibers were observed in the pontine gray, nucleus coeruleus, marginal nucleus of the brachium conjunctivum, nucleus of the solitary tract, inferior olive, and in the tegmental fields..  

The weak NCAM gradient in the pontine migratory stream may contribute to formation of the pontine cell strand and the basal pontine gray..  

Horseradish peroxidase injections into the lateral geniculate nucleus, the lateral posterior nucleus, the opposite superior colliculus, the dorsal lateral pontine gray nucleus, and two descending pathways--the crossed predorsal bundle and the tecto-ponto-bulbar tracts--each labeled SC neurons that were also labeled by PV.  

Transplant fibers were also observed to descend through the caudate putamen in the dispersed fiber bundles of the internal capsule to distribute as terminal branches and varicose fibers within the mesencephalic periaqueductal gray, red nucleus, deep mesencephalic nucleus, and intermediate gray of the superior colliculus, as well as in the pontine gray.  

In the pons, cabp(+) cells and neuropil could be seen in the medial and lateral pontine nuclei (pontine gray).  

Efferent fibers are distributed to a sector of the deep mesencephalic nucleus just dorsolateral to the red nucleus, the basilar pontine gray, posterior and olivary pretectal nuclei, superficial layers of the superior colliculus, lateral posterior thalamic nucleus, ventral lateral geniculate nucleus and zona incerta.  

In the postnatal day (P) 0.5 mouse, labeled pyramidal tract fibers pass through the internal capsule and cerebral peduncle, grow over the basilar pontine gray, and enter into the medullary pyramid (in this study, P0 refers to the first 24 hours after birth). Small collateral branches arise from these pyramidal tract fibers on P0.5-1.0, and elongate quickly into the basilar pontine gray around P2-4. These collateral branches give off many secondary branches on P4 and form the bright terminal zone in the rostral portion of the lateral basilar pontine gray on P9.  

In order to demonstrate possible extrinsic sources of glutamate-immunoreactive axon terminals within the pontine gray, injections of wheat germ agglutinin-horseradish peroxidase were made directly into the basilar pons.  

We have demonstrated previously that visual and auditory inputs reach the rat paraflocculus via dorsolateral pontine gray from the secondary regions of the visual and auditory cortices.  

It is suggested that the immunolabeled neuronal somata and dendrites observed in the rat basilar pontine nuclei represent a population of pontine local circuit neurons; however, it is known that GABAergic cell groups extrinsic to the pontine gray provide afferent projections to the basilar pons, and therefore at least some immunoreactive axon terminals present in the pontine nuclei are derived from these extrinsic sources.  

Following iontophoretic injection of Phaseolus vulgaris in the rat posterior thalamic nucleus (PT) dense terminal fields were labeled in the ipsilateral red nucleus, zona incerta, intermediate and deep layers of the superior colliculus, pretectum, basilar pontine gray, and dorsal pole of the caudal division of the ventral lateral thalamic nucleus.  

Conversion of GU values to standard scores showed abnormalities in dt compared with both control groups in the following areas: deep cerebellar nuclei, locus coeruleus, pontine gray, ventrolateral-ventromedial thalamic complex, nucleus of the third nerve, lateral habenula, and basolateral amygdala.  

A parapharyngeal surgical approach was used to allow the injection micropipette to enter the BPN from the ventral aspect of the brainstem and thus avoid any potential for false-positive labeling due to transection and injury-filling of axonal systems located dorsal to the basilar pontine gray.  

Medium-size, moderately stained neurons that had round large nuclei and no visible cell processes were found in the subthalamic nucleus, pontine gray, trapezoid body, and infratrigeminal, cochlear, and vestibular nuclei.  

Radioactive materials were found in the pulvinar nucleus(Pul), parabigeminal nucleus(PB) and dorsal lateral pontine gray(DLP).  

Small, dense terminal patches were seen in the ipsilateral pontine gray, mostly along the medial and dorsal borders of these nuclei but occasionally in central and dorsolateral regions.  

Thus, as a result, in the medulla and pons, labeled neurons are found in the medial, lateral, and superior vestibular nuclei, the medullary reticular formation including the nucleus reticularis gigantocellularis, the lateral reticular nucleus, the nucleus raphe magnus, the spinal nucleus of V, the nucleus gracilis/nucleus cuneatus, the dorsal and ventral divisions of the parabrachial nucleus, the central pontine gray, the nucleus K of Meessen and Olszewski, and the dorsal nucleus of the lateral lemniscus.(ABSTRACT TRUNCATED AT 400 WORDS).  

The data obtained support the importance of nucleus of pontine gray proper for mediating cerebral signals to cerebellum via brachium pontis..  

We used an antibody raised against the inhibitory transmitter gamma-aminobutyric acid (GABA) in the basilar pontine gray (bpg) of the monkey.  

More caudal projections reach the central gray, superior colliculus and pontine gray.  

Sequential thymidine radiograms from rats injected on days E16, E17, E18, and E19 and killed 2 hours after injection and at daily intervals up to day E22 were used to establish the site of origin, migratory route, and settling patterns of neurons of the nucleus reticularis tegmenti pontis and basal pontine gray. Unlike the neurons of all the other precerebellar nuclei, the basal pontine gray neurons derive from the secondary precerebellar neuroepithelium. The secondary precerebellar neuroepithelium forms on day E16 as an outgrowth of the primary precerebellar neuroepithelium, and it remains mitotically active through day E19, spanning the entire period of basal pontine gray neurogenesis. In the basal pontine gray the sequentially generated neurons settle in a precise order.  

Finally, the secondary precerebellar neuroepithelium produces the latest generated neurons of the basal pontine gray that follow the anterior extramural stream and settle ipsilaterally..  

The labeled fibers passed ventral in the midline to the pontine gray, then laterally through the gray and into the middle cerebellar peduncle to terminate as mossy fibers primarily in the flocculus, lobulus simplex, and Crus I of the ansiform lobule.  

The pontine gray and the nucleus reticularis tegmenti pontis showed a relatively high density of CCK-8 receptor specific binding.  

With the brainstem, labeled fibers distributed to the pontomedullary reticular formation, the locus coeruleus, the raphe pontis, the pontine nuclei, and the dorsolateral tegmental nucleus and adjacent regions of the pontine gray.  

The first brainstem areas innervated by cortical axons are the mesencephalic and rostral pontine tegmentum and parts of the pontine gray adjacent to the pyramidal tract (EPD 29). By EPD 31, cortical axons project to additional areas of the pontine gray, the gigantocellular reticular formation, the medial accessory olive, and the cuneate nucleus.  

Although generally similar to the adult BPN cytoarchitectonically, cell density in the early neonate is substantially higher than in the adult and this obscures to some degree the various subdivisions of the pontine gray.  

Although a great deal of information is available regarding the anatomy of this region, the identity of the neurotransmitter(s) contained in the neurons of the pontine gray are not known.  

The somatotopic distribution of dorsal column nuclear projections within the basilar pontine gray was examined in relation to the massive corticopontine projection system that emanates most heavily from motor and somatosensory cortex. A somatotopic distribution of fore- and hindlimb corticopontine fibers were found in discrete regions of the ipsilateral pontine gray. Similarly, pontine afferents from the dorsal column nuclei terminated somatotopically in the caudal half of the contralateral pontine gray in that gracilopontine fibers distributed caudal to cuneopontine fibers.  

ruber, anterodorsolateral midbrain tegmentum, superior and inferior colliculi, pontine gray, cerebral peduncles, medial pontine reticular formation, raphe and vestibular nuclei did not affect the acoustic structure of the calls tested.  

The results are discussed in the context of these projections modulating ascending visual information (claustrum, lateral intermediate nucleus, pulvinar, dorsal lateral geniculate, cells of the external medullary lamina, reticular nucleus of the thalamus, superficial collicular layers, and the anterior and posterior pretectal nuclei) or visuomotor information (putamen, caudate, ventral lateral geniculate, pontine gray, and the anterior and posterior pretectal nuclei)..  

The projections from the cerebellar lateral and interposed nuclei onto the basilar pontine gray and nucleus reticularis tegmenti pontis (NRTP) have been studied in the rat by the use of the autoradiographic technique. In the pontine gray proper, fibers from the lateral nucleus are distributed to three rostrocaudally oriented columns: (i) in the medial nucleus, (ii) in the ventral nucleus, and (iii) in the dorsolateral and lateral nuclei.  

The greatest accumulation of labeled terminals was noted in the ventrolateral and lateral border regions of the BPN while a slightly less dense aggregation was observed along the ventral, ventromedial and midline regions of the pontine gray. However, small fascicles of labeled axons were seen to course ventrally around the dorsolateral aspect of the cerebral peduncle to reach lateral pontine areas while other labeled axons descended through clefts in the mid-portion of the cerebral peduncle or passed through the medial lemniscus and around the medial portion of the cerebral peduncle to enter the pontine gray..  

Morphology, microtopography and numerical density of oligodendrocytes were analyzed by light microscopy in the pontine gray and middle cerebellar peduncle of adult cats. The cell morphology did not co-vary with any of these groups, but the shape of oligodendrocytes was on an average more elongated in the peduncle than in the pontine gray. Axon bundles within the pontine gray contained only very few oligodendrocytes (density 6% that of the peduncle).  

In pontine gray matter, n.  

The medial portion of the nucleus reticularis tegmenti pontis (NRTP), considered to be a tegmental extension of the basilar pontine gray, also received its principal cortical input from the frontal lobe.  

Such lesions, when placed in the basilar pontine gray using a dorsal approach, resulted in the degeneration of nearly the entire population of mossy fiber varicosities within the contralateral ansiform lobule.  

ruber, reticular formation of midbrain, pons and medulla, the pontine gray and nucl .  

Results revealed that dorsal column nuclear projections to the contralateral pontine gray terminate predominantly in two regions--one in the caudal aspect of the medial pontine subdivision and another overlapping the ventral and lateral subdivisions. Spinal trigeminal projections terminated most heavily within the contralateral pontine gray at midpontine levels. In comparison to the above-mentioned pontine afferents, both high cervical and midthoracic spinal cord lesions produced a similar pattern of axonal degeneration in the ipsilateral pontine gray which overlapped substantially with gracilis inputs. The observed topographic distribution pattern of ascending afferents to pontine gray confirm and extend previous findings which in general have only briefly described these pathways..  

Caudal to the stimulation site, increases in glucose utilization were found in the midline dorsal raphe, the ipsilateral pontine gray, medial parabrachial nucleus, and the locus coeruleus.  

The remodelling of right SMP projections after neonatal left SMC lesions demonstrates an interaction between corresponding pathways originating from opposite sides of the brain and which occurs in response to the partial removal of afferents to pontine gray neurons as a result of the SMC lesions.  

Locally, significant reversal effects by DN-1417 were observed in the hypothalamus, septal nucleus, hippocampus, mammillary body, thalamus dorsomedial nucleus, caudate-putamen, nucleus accumbens, pontine gray matter and so on.  

Fascicles of cerebellopontine axons left the main bundle of descending limb fibers throughout much of the rostrocaudal length of the BPN and passed around and through the medial lemniscus and cerebral peduncle to enter the pontine gray.  

In the pontine gray, the bulk of the projection concerns the dorsal aspect of the medial nucleus.  

Autoradiographic experiments showed that the incertofugal fiber systems reach ipsilaterally to the thalamus (lateral dorsal, central lateral, ventral lateral geniculate, parafascicular, subparafascicular and reuniens nuclei, and posterior nuclear complex), to the hypothalamus (dorsal, lateral and posterior hypothalamic areas), to the tectum (medial pretectal area, deep pretectal and pretectal nuclei, superior colliculus and periaqueductal gray) and to the midbrain tegmentum, pons and medulla oblongata (subcuneiform, cuneiform and red nuclei, nuclei of the posterior commissure and Darkschewitsch, interstitial nucleus of Cajal, pedunculopontine tegmental nucleus, oral and caudal pontine reticular nuclei, nucleus raphe magnus, gigantocellular reticular nucleus, pontine gray and inferior olivary complex).  

The absence of contralateral inferior olive and of ipsilateral middle peduncle, together with a marked regression of the contralateral pontine gray, were indicative of successful pedunculotomy.  

The majority of labeled cells were characteristically distributed along the medial, ventral, and lateral perimeters of the pontine gray. Similarly, the pattern of labeling following injections into the paramedian lobule largely avoided the medial and lateral perimeters of the pontine gray, while numerous labeled somata occupied the central region of the pons.  

Lobule VIII receives afferents from the caudal aspect of the pontine gray.  

Routine autoradiographic studies in the first group revealed abnormally dense axonal and terminal labeling in the pontine gray contralateral to the leucine-injected hemisphere, suggesting that much of the label was due to sprouting from intact corticopontine axons into the neonatally deafferented pontine gray. In the group with a second (adult) cortical lesion contralateral to the neonatal ablation, degenerating axons and boutons were abundant in the pontine gray contralateral to the adult lesion and at least some of these were interpreted to represent sprouted corticopontine axons and their terminals..  

A well-organized topography of projections was observed with anterior cingulate cortex projecting to the medial part of the pontine gray matter and posterior cingulate cortex projecting to the lateral part. Together these projections form a circle of termination around the periphery of the pontine gray matter..  

The basilar pontine gray in adult rats was subjected to electron microscopic examination in order to characterize: 1) certain general cytologic features, 2) the principle categories of presynaptic profiles, and 3) the postsynaptic targets of the various categories of presynaptic boutons.  

Deep efferent fibers ran rostrally and caudally in the central gray, and in some cases laterally directed fibers were seen to distribute in the midbrain tegmentum and reticular formation, in one case reaching the pontine gray.  

Neuronal necrosis with karyorrhexis and proliferative changes in astrocytes are most prominent in the pontine gray matter and subiculum of the hippocampus.  

Locally, significant depression was observed in the following structures: frontal and visual cortices, hippocampus Ammon's horn and dentate gyrus, medial and lateral geniculate bodies, nucleus accumbens, caudate-putamen, substantia nigra, pontine gray matter, superior colliculus, superior olivary nucleus, vestibular nucleus, lateral lemniscus and cerebellar cortex.  

The present study shows that 3--5 days following lesions of the dentate and interposed nuclei in normal adult rats degenerating axons and axon terminals can be detected in the contralateral pontine gray. Other complex synaptic structures are also present in both the right and left pontine gray in the experimental animals. Occasional features of neuronal reaction could still be seen in both sides of the pontine gray for as long as 3--6 months after the neonatal cerebellar lesions..  

In many structures, cessation of EEG activity was accompanied by a further increase in 1-CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400--500% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed.  

min-1 for cochlear nucleus: 3.0 for inferior colliculus; 2.5 for medical geniculate; 1.9 for pontine gray and hypothalamus; 1.7 for caudate and cerebral cortex; and 1.2 for cerebellar gray and 0.41-0.50 for white matter structures.  

However, axonal degeneration and not radioactive label were observed in the mediodorsal thalamus, the superior colliculus, the medial pontine gray, the mesencephalic nucleus of the Vth nerve, the motor nucleus of V, the raphe nuclei and the crus cerebri fiber system.  

Crus I and crus II of the cerebellar hemispheres received a bilateral projection which also included neurons distributed in mirror image locations in both halves of the pontine gray.  

Two types of neurons, projection and intrinsic, previously identified in Golgi preparations of the adult monkey (Macaca mulatta) basilar pontine gray (Cooper and Fox, '76) were observed electronmicroscopically in Macaca mulatta and the squirrel monkey Saimiri sciureus. Following unilateral cortical ablations both dark and filamentous degeneration were observed in the ipsilateral basilar pontine gray..  

Observations from Golgi material indicate that principal neurons whose primary axons project to the cerebellar cortex may also give rise to recurrent branches distributing within the pontine gray.  

This pattern was found to be essentially similar to earlier studies and corroborated more recent reports of projections to the pontine gray and inferior olivary nuclei. These animals also demonstrated an absence of cells in the pontine gray and inferior olive on the side contralateral to the hemicerebellectomy and in the lateral reticular and lateral cuneate nuclei on the ipsilateral side..  

Cerebellofugal fibers of the B.C.de terminate in a distinctive pattern within precerebellar brainstem nuclei: densely throughout the middle third of nucleus reticularis tegmenti pontis; in a longitudinal zone of each of the three pontine gray subnuclei; in the principal and dorsal accessory nuclei of the inferior olive; and sparsely within nucleus reticularis paramedianus.  

Following removal of a significant part of the dentate nucleus and most of the interpositus nucleus in the rat cerebellum degenerated cerebellopontine fibres are shown to end in three fairly restricted regions in the contralateral pontine gray: in the paramedian position, in the middle and in the lateral third.  

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.  

In Golgi preparations of the adult monkey (Macaca mulatta) two types of neurons are distinguished in the pontine gray: (1) larger neurons which impregnate most frequently and (2) smaller neurons which impregnate rarely. The former are judged to be projection neurons with myelinated axons because only the initial segments of their axons impregnate, while the latter are judged to be intrinsic neurons since they appear to participate only in the local circuitry of the pontine gray.  

The most caudal terminal field was found in the medial pontine gray.  

In addition, certain regions of the brain such as the reticular formation and pontine gray receive diffuse DBH innervation derived from less clearly defined pathways.  

The cells in the pontine gray which give origin to fibers to the paramedian lobule lie together, in part in groups, and in part in columns.  

Neurons in other reticular tegmental fields, the tegmental reticular nucleus and pontine gray, show a more sustained or tonic discharge pattern.  

Neurons within the basilar pontine gray (BPG) of the American opossum can be subdivided into four major nuclei which are named medial, lateral, ventral and peripeduncular in accordance with previous studies. In one case with a cortical lesion restricted to the motor-sensory cortex, mainly dark degenerating terminals are apparent in the ipsilateral pontine gray, whereas in a lesion confined to the visual cortex only filamentous degeneration was observed.  

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