Projections from the intracerebellar nuclei to the ventral midbrain tegmentum in the rat

The present study was undertaken to provide anatomical evidence, in the rat, for a direct projection from the cerebellum towards structures, other than the red nucleus, which belong to the ventral midbrain tegmentum, by using the retrograde as well as the anterograde horseradish peroxidase transport method. Following unilateral injection in the ventral midbrain tegmentum of horseradish peroxidase, free or conjugated to wheat germ agglutinin, sparing the red nucleus, retrogradely labeled neurons were found in the contralateral cerebellar lateral nucleus and, at lower density, in the interpositus nucleus. No labeled neurons were found in the fastigial nucleus of either side. Anterogradely labeled axons from lectin coupled horseradish peroxidase injection sites in the lateral and interpositus nuclei reached the contralateral ventral midbrain tegmentum. Terminal labeling was observed in the entire red nucleus as well as in the lateral division of the ventral tegmental area of Tsai, in the dorsal region of the substantia nigra pars compacta, and in the medial part of the retrorubral field. No terminal labeling was found in the caudal linear nucleus, interfascicular nucleus, peripeduncular nucleus, rostral linear nucleus of the raphe, substantia nigra pars lateralis and the substantia nigra pars reticulata. Terminal labeling was also not observed in the ventral midbrain tegmentum following horseradish peroxidase injection in lateral and interpositus nuclei of rats pretreated with kainic acid. In conclusion, it is noteworthy that, besides the red nucleus, the sole structures of ventral midbrain tegmentum receiving cerebellar efferents are those with a higher density of dopaminergic cells.     

A lectin horseradish peroxidase study of the origin of ascending fibers in the medial forebrain bundle of the rat. The upper brainstem

The origins of projections within the medial forebrain bundle from the upper brainstem were examined with the horseradish peroxidase technique. Labeled cells were found in approximately 15 upper brainstem nuclei following injections of a conjugate of horseradish peroxidase and wheat germ agglutinin at various levels of the medial forebrain bundle. Labeled nuclei included (from caudal to rostral): dorsal and ventral parabrachial nuclei; Kolliker-Fuse nucleus; dorsolateral tegmental nucleus; A7 (lateral pontine tegmentum medial to lateral lemniscus); median and dorsal raphe nuclei; distinct group of cells oriented mediolaterally in the dorsal pontine tegmentum below the central gray; B9 (ventral midbrain tegmentum dorsal to medial lemniscus); retrorubral nucleus; nucleus of Darkschewitsch, interfascicular nucleus; rostral and caudal linear nuclei; ventral tegmental area; medial part of substantia nigra, pars compacta; and the supramammillary nucleus. With the exception of the ventral parabrachial nucleus, Kolliker-Fuse, A7, B9 and substantia nigra, pars compacta, each of the nuclei mentioned above sent strong projections along the medial forebrain bundle to the rostral forebrain. Sparse labeling was observed throughout the pontine and midbrain reticular formation. With the exception of the dorsal raphe nucleus, projections to the most anterior regions of the medial forebrain bundle (level of the anterior commissure) essentially only arose from presumed dopamine-containing nuclei-retrorubral nucleus (A8 area), interfascicular nucleus, rostral and caudal linear nuclei, substantia nigra pars compacta, and ventral tegmental area. Evidence was reviewed indicating that major forebrain sites of termination for these dopaminergic nuclei are structures that have been collectively referred to as the 'ventral striatum'. It is concluded from the present findings that several pontine and mesencephalic cell groups are in a position to exert a strong, direct effect on structures in the anterior forebrain and that the medial forebrain bundle is the main communication route between the upper brainstem and the forebrain.     

Ascending projections of presumed dopamine-containing neurons in the ventral tegmentum of the rat as demonstrated by horseradish peroxidase

The projections of presumed dopamine-containing neurons in the zona compacta of the substantia nigra and the ventral tegmental area were examined by stereotaxic injections of horseradish peroxidase into diverse cortical and subcortical regions which are known to include dopamine-containing terminals. Neurons in the lateral half of the substantia nigra pars compacta were labelled after injections into the caudolateral aspect of the caudate-putamen, while neurons in the medial part of the substantia nigra pars compacta and lateral aspect of the ventral tegmental area projected to the anteromedial portion of the caudate putamen. Injections of horseradish peroxidase into the amygdala resulted in the appearance of reactive neurons in the anterior portion of the ventral tegmental area, but the more caudally located entorhinal cortex received projections from the posterior half of the ventral tegmental area. Injections of horseradish peroxidase into the frontal cortex, anterior to the genu, produced scattered labelled cells in the rostral half of the ventral tegmental area, whereas more posterior injections into the cingulate cortex resulted in the appearance of reactive cells which were confined to the medial one-quarter of the substantia nigra pars compacta. The near-midline structure, the lateral septum, was innervated by neurons with cell bodies primarily in the medial half of the ventral tegmental area. Injections of horseradish peroxidase into the nucleus accumbens, which contains very high levels of dopamine, resulted in the appearance of many labelled neurons throughout the ventral tegmental area and some reactive neurons in the medial part of the substantia nigra pars compacta. A few labelled cells were also occasionally observed in the contralateral ventral tegmental area after accumbens injections.These results suggest that although there is considerable overlap, and that the same subdivisions within the substantia nigra pars compacta and the ventral tegmental area appear to innervate diverse regions of the forebrain, there also exists a general topographical organization with respect to the projections of these neurons.Injections of horseradish peroxidase into some of the forebrain regions also resulted in the appearance of reactive cells in mesencephalic nuclei not known to contain dopaminergic perikarya. For example, labelled cells were observed in the supramamillary nucleus after injections into the frontal cortex, entorhinal cortex, accumbens and lateral septum. Injections into the amygdala produced reactive cells in the suprageniculate nucleus, the peripeduncular nucleus, and the magnocellular nucleus of the medial geniculate. These latter results are discussed with reference to the possibility that such pathways may mediate the responsiveness of cells in the amygdala to a wide range of sensory stimuli.     

Corticonigral projections from area 6 in the raccoon

Summary The corticonigral projections from area 6 in the raccoon were investigated using the autoradiographic tracing method. Injections of tritiated proline and leucine were made into either medial or lateral area 6 subdivisions. Uniformly distributed silver grains were observed overlying the ipsilateral substantia nigra pars compacta (SNc) while more restricted foci of label indicative of fiber labeling were present in the substantia nigra pars reticulata (SNr). Autoradiographic label was also present in the substantia nigra pars lateralis (SNl), the retrorubral area and the ventral tegmental area of Tsai. The existence of corticonigral projections from area 6 may serve to modulate SNc activity as a whole and provide an important substrate for the cerebral control of movement.Abbreviations cp cerebral peduncle - IP interpeduncular nucleus - PG pontine gray - R red nucleus - RR retrorubral area - SNc substantia nigra, pars compacta - SNl substantia nigra, pars lateralis - SNr substantia nigra, pars reticularis - VTA ventral tegmental area     

Basal ganglia and other afferent projections to the peribrachial region in the rat: A study using retrograde and anterograde transport of horseradish peroxidase

The afferent projections to the peribrachial region in the rat were studied using retrograde and anterograde transport of horseradish peroxidase. Particular attention was paid to descending projections from the basal ganglia and related nuclei to the region of nucleus tegmenti pedunculopontinus. Following injection of peroxidase into nucleus tegmenti pedunculopontinus, few retrogradely-labelled neurons were found in the entopeduncular nucleus proper, but larger numbers were found with a wide distribution within the boundaries of the internal capsule and cerebral peduncle. Labelled cells were also consistently observed in the amygdala, the caudal globus pallidus, the subthalamus including zona incerta and subthalamic nucleus, the hypothalamus, the substantia nigra and the ventral tegmental area. Following iontophoretic injections of horseradish peroxidase into the entopeduncular nucleus, lateral hypothalamus, subthalamic nucleus or ventral tegmental area, terminal labelling was observed in and around the branchium conjunctivum in an area apparently corresponding to nucleus tegmenti pedunculopontinus in the rat.     

Projections to gyrus sigmoideus from the substantia nigra in the cat,as revealed by the horseradish peroxidase retrograde transport technique

After injections of horseradish peroxidase in the gyrus sigmoideus of the cat frontal cortex, labelled neurones were found in the substantia nigra and the ventral tegmental area of Tsai. Neurones distributed bilaterally clearly predominated in the side of the injection in the rostral sections, but differences in number were less at caudal levels. The present findings confirm the existence of a direct mesencephalocortical projection from this ventral tegmental region, and provide a morphological substrate for a better understanding of the role of the dopaminergic systems in the motor cortical regulation.     

Topographical organization of the nigrotectal projection in rat: evidence for segregated channels.

Recent evidence suggests that projections from the superior colliculus to the brainstem in rat are organized into a series of anatomically segregated output channels. To understand how collicular function may be modified by the basal ganglia it is important to know whether particular output modules of the superior colliculus can be selectively influenced by input from substantia nigra. The purpose of the present study was, therefore, to examine in more detail topography within the nigrotectal system in the rat. Small injections (10-50 nl) of a 1% solution of wheatgerm agglutinin conjugated with horseradish peroxidase were made at different locations within substantia nigra and surrounding structures. A discontinuous puff-like pattern of anterogradely transported label was found in medial and caudal parts of the ipsilateral intermediate layers of the superior colliculus. In contrast, the rostrolateral enlargement of the intermediate layers contained a greater density of more evenly distributed terminal label. Injection sites associated with this dense pattern of laterally located label were concentrated in lateral pars reticulata, while the puff-like pattern was produced by injections into ventromedial pars reticulata. Retrograde tracing experiments with the fluorescent dyes True Blue and Fast Blue revealed that injections involving the rostrolateral intermediate layers were consistently associated with a restricted column of labelled cells in the dorsolateral part of ipsilateral pars reticulata. Comparable injections into medial and caudal regions of the superior colliculus produced retrograde labelling in ventral and medial parts of the rostral two-thirds of pars reticulata. Both anterograde and retrograde tracing data indicated that contralateral nigrotectal projections arise from cells located in ventral and medial pars reticulata. The present results suggest that the main ipsilateral projection from substantia nigra pars reticulata to the superior colliculus comprises two main components characterized by regionally segregated populations of output cells and spatially separated zones of termination. Of particular interest is the apparent close alignment between terminal zones of the nigrotectal channels and previously defined populations of crossed descending output cells in the superior colliculus. Thus, the rostrolateral intermediate layers contain a concentration of terminals specifically from dorsolateral pars reticulata and output cells which project to the contralateral caudal medulla and spinal cord. Conversely, the medial and caudal intermediate layers receive terminals from ventral and medial pars reticulata and contain cells which project specifically to contralateral regions of the paramedian pontine and medullary reticular formation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nucleus tegmenti pedunculopontinus: Efferent connections with special reference to the basal ganglia,studied in the rat by anterograde and retrograde transport of horseradish peroxidase

The efferent connections of the brain stem nucleus tegmenti pedunculopontinus were studied in the rat using the techniques of anterograde and retrograde transport of the enzyme horseradish peroxidase, laying particular emphasis on that part of pedunculopontinus which receives direct descending projections from the basal ganglia and related nuclei. In a preliminary series of experiments horseradish peroxidase was injected into either the entopeduncular nucleus or the subthalamic nucleus and, following anterograde transport of enzyme, terminal labelling was identified in nucleus tegmenti pedunculopontinus, surrounding the brachium conjunctivum in the caudal mesencephalon.In a subsequent series of experiments, horseradish peroxidase was injected into that region of nucleus tegmenti pedunculopontinus which receives entopeduncular and subthalamic efferents and its efferent projections were studied by anterograde transport of the enzyme. The results indicate that nucleus tegmenti pedunculopontinus gives rise to widely distributed efferent projections which terminate rostrally in mesencephalic, diencephalic and telencephalic structures and caudally in the pontine tegmentum. In the mesencephalon, terminal labelling was found in the pars compacta of the ipsilateral substantia nigra and sometimes in the adjoining ventral tegmental area. Labelling was also found in the ipsilateral half of the periaqueductal grey. In the diencephalon terminal labelling occurred bilaterally in the subthalamic nucleus and ipsilaterally in the intralaminar nuclei of the thalamus. Further rostrally, terminal labelling was particularly evident in the ipsilateral pallidal complex, especially in the caudal two-thirds of the entopeduncular nucleus and the ventral half of the caudal third of the globus pallidus. Caudal to pedunculopontine injection sites dense labelling was observed in the reticular formation of the pontine tegmentum.In a final series of experiments, confirmation of apparent pedunculopontine efferent projections was sought using the retrograde transport of horseradish peroxidase. Enzyme was injected into sites possibly receiving pedunculopontine efferents and the peribrachial area of the brain stem was examined for retrograde cell labelling. In this way, pedunculopontine projections were confirmed to the globus pallidus, entopeduncular nucleus, subthalamic nucleus, substantia nigra, parafascicular nucleus and pontine reticular formation. Injections into the globus pallidus or subthalamic nucleus gave rise to retrograde cell labelling bilaterally in pedunculopontinus. In addition, retrograde transport studies alone demonstrated projections from pedunculopontinus to the cerebral cortex and to the spinal cord.It is concluded that the nucleus tegmenti pedunculopontinus has reciprocal relationships with parts of the basal ganglia and some functionally related nuclei (in particular, the pallidal complex, subthalamic nucleus and substantia nigra). These connections support the view that nucleus tegmenti pedunculopontinus is likely to be involved in the subcortical regulation and mediation of basal ganglia influences upon the lower motor system. This suggests a potential role for pedunculopontine afferent and efferent pathways in the pathophysiology of basal ganglia related disorders of movement.     

The afferent connections of the inferior olivary complex in rats: A study using the retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase (HRP) was used to define the origin of afferents to the inferior olivary complex (IOC) in rats. Using both ventral and dorsal surgical approaches to the brainstem, HRP was injected into the IOC through a micropipette affixed to the tip of a 1-μl Hamilton syringe. After a 2-day postoperative survival, animals were sacrificed by transcardiac perfusion with a 1% paraformaldehyde-1.25% gluteraldehyde solution, and brains were processed according to the DeOlmos protocol (1977), using o-dianisidine as the chromogen. Labeled cells were found at many levels of the nervous system extending from lumbar spinal cord to cerebral cortex. This wide-ranging input from numerous regions clearly underscores the complexity of the IOC and its apparent involvement in several functions. Within the spinal cord, labeled neurons were identified from cervical to lumbar but not at sacral levels. These neurons were found contralaterally in the neck region of the dorsal horn and in the medial portions of the intermediate gray. In the caudal brainstem, reactive cells in the dorsal column nuclei, the spinal trigeminal nucleus, and the subnucleus y of the vestibular complex were observed primarily contralateral to the injection sites. Labeling within the gigantocellular, magnocellular, ventral, and lateral reticular nuclei and the nucleus prepositus hypoglossi was primarily ipsilateral. Reactive neurons in the medial and inferior vestibular nuclei were predominantly ipsilateral or contralateral to HRP injections into the caudal or rostral IOC, respectively. The dentate and interposed nuclei of the cerebellum contained small, lightly labeled neurons primarily contralateral to the injection site, while the fastigial nuclei contained a few relatively large, heavily labeled cells bilateral to caudal olivary injections. Ipsilaterally labeled mesencephalic regions included the periaqueductal gray, interstitial nucleus of Cajal, rostromedial red nucleus, ventral tegmental area, medial terminal nucleus of the accessory optic tract, nucleus of the optic tract, and the lateral deep mesencephalic nucleus. The caudal part of the pretectum and small cells of the stratum profundum of the superior colliculus were labeled predominantly contralateral to the injection. In the caudal diencephalon labeled neurons were most numerous within the nucleus of Darkschewitsch and the subparafascicular nucleus, primarily ipsilateral to olivary injections. Scattered reactive neurons were also found within the ipsilateral zone incerta. With the exception of the zona incerta, all labeled mesencephalic and diencephalic nuclei had some bilateral representation of labeled cells. No labeled neurons were identified within the basal ganglia, while numerous reactive cells were found bilaterally within layer V of the frontal and parietal cerebral cortex.     

Basal ganglia projections to the brain stem in the lizard Varanus exanthematicus as demonstrated by retrograde transport of horseradish peroxidase

In the present study the cells of origin of basal ganglia projections to the brain stem have been studied with the horseradish peroxidase technique in the lizard, Varanus exanthematicus. Injections of horseradish peroxidase were made at various levels of the brain stem from the mesodiencephalic border to the obex as well as in the tectum mesencephali. Efferent libers from the telencephalon to the diencephalon and the brain stem were found to arise predominantly from the striatum. From the present data it seems likely that the basal ganglia in Varanus exanthematicus as in other reptiles consist of two parts, a rostral ‘striatal’ part with projections mainly to the diencephalon and mesencephalon including the substantia nigra and a caudal ‘pallidal’ part with projections to the intercollicular nucleus and the rhombencephalic reticular formation.Injections of horseradish peroxidase into various parts of the rhombencephalic reticular formation have shown rather extensive projections from diencephalic and mesencephalic structures which receive afferents from the striatum: the posterior entopeduncular nucleus, the intercollicular nucleus and the substantia nigra were found to project as far caudal as the nucleus reticularis inferior. The substantia nigra shows, as regards its fiber connections, striking similarities to the mammalian substantia nigra, whereas the intercollicular nucleus possibly represents the reptilian homologue of the mammalian pedunculopontine nucleus.Injections of horseradish peroxidase into the tectum mesencephali have shown labeled cells in the nucleus of the posterior commissure, the posterior entopeduncular nucleus and the substantia nigra, all centers which are known to receive afferents from the striatum. Thus, the striatum can influence bisynaptically the reptilian homologue of the mammalian superior colliculus.It can be concluded that the striatum of the lizard, Varanus exanthematicus, has extensive direct as well as indirect projections to centers which influence the motor apparatus of the brain stem and spinal cord. Thus in reptiles it seems likely that the striatum exerts its influence on motor activity mainly via descending projections, in contrast to mammals where both descending and ascending striatal efferent pathways occur.     

Pontine and mesencephalic afferents to the central nucleus of the amygdala of the rat

The pontine and mesencephalic afferent connections to the central nucleus of the amygdala have been studied by means of the retrograde transport of horseradish peroxidase (HRP). In the pons, labeled neurons were consistently found in the dorsal raphe nucleus and the parabrachial nucleus. In the mesencephalon, labeled cells were consistently found in the ventral tegmental area, the substantia nigra and the peripeduncular nucleus.     

Biochemical evidence for γ-aminobutyrate containing fibres from the nucleus accumbens to the substantia nigra and ventral tegmental area in the rat

Glutamate decarboxylase activity, a specific marker for γ-aminobutyrate-containing neurons, has been analysed in microdissected samples from rat mesencephalon following unilateral electrocoagulations of the nucleus accumbens. This lesion resulted in a consistent decrease of 50% in the enzyme activity in the rostromedial substantia nigra, and a slight, but insignificant decrease (?15%) in the medial parts of the caudal pars compacta of the substantia nigra. No change was found in the lateral pars compacta or the central pars reticulata. In the ventral tegmental area, the highest activity was found in the rostromedial part, adjacent to the mammillary body. At this level, a significant decrease of 20% was found in the ventral tegmental area on the lesioned side. In contrast, the activities in the medial accessory optic nucleus and the caudal ventral tegmental area adjacent to the interpenduncular nucleus were unchanged.The results indicate that the nucleus accumbens sends γ-aminobutyrate-containing fibres to the rostromedial substantia nigra and to the rostral ventral tegmental area. The caudal ventral tegmental area, the lateral pars compacta and the central pars reticulata do not receive measurable amounts of such fibres.     

猫丘脑中央外侧核的皮质下传入联系

本实验用HRP逆行性轴浆运输技术,对猫丘脑中央外侧核的传入纤维联系及其局部定位关系进行了观察。投射至丘脑中央外侧核尾侧区的主要核团包括:外侧膝状体腹核背侧带、丘脑网状核特别是它的背侧部、上丘深层,以同侧为主。板内核、丘脑下部外侧区和黑质网状部神经元的轴突终止在同侧丘脑中央外侧核吻侧区。丘脑中央外侧核全长的传入起自脑干网状结构和前庭神经核,呈双侧投射。前者以同侧为主,后者以对侧占优势。同侧未定带,顶盖前区、动眼神经核周围的细胞群、对侧三叉神经感觉主核、楔束核、薄束核以及小脑齿状核内也含有少量标记细胞。我们还观察到HRP注射中心区位于中央外侧核并扩散至丘脑腹前核者,同侧脚内核含大量HRP阳性细胞,而Gudden被盖腹侧核内充满密集的标记终末。这些结果表明,丘脑中央外侧核可能涉及多种感觉和运动功能。     

Topographic projections from the basal ganglia to the nucleus tegmenti pedunculopontinus pars compacta of the cat with special reference to pallidal projections

Summary Projections from the basal ganglia to the nucleus tegmenti pedunculopontinus pars compacta (TPC) were studied by using anterograde and retrograde tracing techniques with horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) in the cat. Following WGA-HRP injections into the medial TPC area, a substantial number of retrogradely labeled cells were seen in the entopeduncular nucleus (EP) and medial half of the substantia nigra pars reticulata (SNr), whereas following WGA-HRP injections into the lateral TPC area, labeled cells were marked in the caudal half of the globus pallidus (GP) and lateral half of the SNr. To confirm the retrograde tracing study, WGA-HRP was injected into the EP or the caudal GP, and anterograde labeling was observed in the TPC areas. Terminal labeling was located in the medail TPC area in the EP injection case, while terminal labeling was observed in the lateral TPC area in the caudal GP injection case. Projections from the striatum to the pallidal complex (the EP and the caudal GP) were also studied autoradiographically by injecting amino acids into various parts of the caudate nucleus and the putamen. Terminal labeling was distributed over the whole extent of the EP and the rostral GP following injections into the rostral striatum (the head of the caudate nucleus or the rostral part of the putamen), while terminal labeling was distributed over the caudal GP following injections into the caudal striatum (the body of the caudate nucleus or the caudal part of the putamen). From these findings, we conclude that there exists a medio-lateral topography in the projection from the basal ganglia to the TPC: The EP receives afferent projections from the rostral striatum and projects to the medial TPC area, whereas the caudal GP receives projections from the caudal striatum and sends fibers to the lateral TPC area.Abbreviations BC brachium conjunctivum - CD caudate nucleus - CP cerebral peduncle - DBC decussation of the brachium conjunctivum - EP entopeduncular nucleus - GP globus pallidus - IC internal capsule - ICo inferior colliculus - LH lateral habenular nucleus - ML medial lemniscus - PN pontine nuclei - PUT putamen - SCo superior colliculus - SI substantia innominata - SN substantia nigra - SNc substantia nigra pars compacta - SNr substantia nigra pars reticulata - STN subthalamic nucleus - TH thalamus - TPC nucleus tegmenti pedunculopontinus pars compacta     

Subcortical afferents of the nucleus accumbens septi in the cat, studied with retrograde axonal transport of horseradish peroxidase and bisbenzimid

The afferent connections of the nucleus accumbens septi from subcortical centers in the cat were studied with the aid of two different retrograde tracer substances. In most experiments horseradish peroxidase was injected in the nucleus accumbens, either mechanically or by microiontophoresis. In a few cats injections of bisbenzimid were placed and subsequently the retrogradely labelled cells were visualized with fluorescence microscopy. In a number of experiments neighbouring nuclei of the nucleus accumbens were involved in the injection site. Control injections were placed in the nucleus caudatus.With both tracers the same topography of labelled cells could be demonstrated following injections into the nucleus accumbens. Labelled cells were found in the basolateral nucleus of the amygdaloid complex. In the thalamus the nucleus paraventricularis and the nucleus parataenialis were most heavily labelled. Other midline nuclei, which showed fewer labelled cells, included the nucleus interanteromedialis, the nucleus rhomboidalis, the nucleus centralis medialis and the nucleus reuniens. Some projections were also found to originate from the medial part of the parafascicular nucleus. In the mesencephalic tegmentum the ventral tegmental area of Tsai, the interfascicular nucleus and the retrorubral nucleus contained labelled cells. A smaller number of cells was found to be labelled in the substantia nigra proper. In addition, the rostral linear nucleus, the central linear nucleus and the dorsal raphe nucleus, all belonging to the raphe nuclei, showed labelling of cells.A comparison with the distribution of labelled cells following injections into the caudate nucleus showed that the accumbens and caudate nuclei share many projections from the mesencephalon and the thalamus. However, the accumbens can be distinguished from the caudate because it receives afferents from the amygdala.     

Afferents to the basal forebrain cholinergic cell area from pontomesencephalic--catecholamine, serotonin, and acetylcholine--neurons

The afferent input to the basal forebrain cholinergic neurons from the pontomesencephalic tegmentum was examined by retrograde transport of wheatgerm agglutinin-horseradish peroxidase in combination with immunohistochemistry. Multiple tyrosine hydroxylase-, dopamine-beta-hydroxylase-, serotonin- and choline acetyltransferase-immunoreactive fibres were observed in the vicinity of the choline acetyltransferase-immunoreactive cell bodies within the globus pallidus, substantia innominata and magnocellular preoptic nucleus. Micro-injections of horseradish peroxidase-conjugated wheatgerm agglutinin into this area of cholinergic perikarya led to retrograde labelling of a large population of neurons within the pontomesencephalic tegmentum, which included cells in the ventral tegmental area, substantia nigra, retrorubral field, raphe nuclei, reticular formation, pedunculopontine tegmental nucleus, laterodorsal tegmental nucleus, parabrachial nuclei and locus coeruleus nucleus. Of the total population of retrogradely labelled neurons, a significant (approximately 25%) proportion were tyrosine hydroxylase-immunoreactive and found in the ventral tegmental area (A10), the substantia nigra (A9), the retrorubral field (A8), the raphe nuclei (dorsalis, linearis and interfascicularis) and the locus coeruleus nucleus (A6), Another important contingent (approximately 10%) was represented by serotonin neurons of the dorsal raphe nucleus (B7), the central superior nucleus (B8) and ventral tegmentum (B9). A small proportion (less than 1%) was represented by cholinergic neurons of the pedunculopontine (Ch5) and laterodorsal (Ch6) tegmental nuclei. These results demonstrate that pontomesencephalic monoamine neurons project in large numbers up to the basal forebrain cholinergic neurons and may represent a major component of the ventral tegmental pathway that forms the extra-thalamic relay from the brainstem through the basal forebrain to the cerebral cortex.     

Distribution of thalamo-caudate neurons in the cat as demonstrated by horseradish peroxidase

Summary Distribution of thalamocaudate neurons in the cat was examined by means of the horseradish peroxidase (HRP) method. After injection of HRP into the head of the caudate nucleus (Cd), thalamic neurons labeled with HRP were observed mainly in the rhomboid nucleus (Rh), central medial nucleus (Ce), centre médian-parafascicular complex (CM-Pf) as well as in the midline and intralaminar regions surrounding the mediodorsal nucleus (MD). Distribution of HRP-labeled neurons in the centrolateral nucleus (CL) were localized in the medial parts of the nucleus. Many HRP-labeled neurons were also seen in the substantia nigra (SN) and retrorubral nucleus (Rr). Additionally, HRP-labeled neurons were found in the ventrolateral portions of the anteromedial nucleus (AM), lateral portions of the MD, ventral tegmental area of Tsai (vT) and the midline raphe nuclei, such as the rostral lineal (rL), central lineal (cL) and dorsal raphe (dR) nuclei.     

大鼠眶皮质的间脑和脑干的传入投射

目的：研究间脑和脑干对眶皮质的传入投射。方法：ＨＲＰ逆行示踪法。结果：将ＨＲＰ分别导入１８只大鼠的内侧及腹侧眶区、腹外侧内和外侧区后，在同侧丘脑背内侧核中可见密集的标记细胞，并有一定的局部定位，其次在内丘脑的胶状核、前内侧核、菱形核、腹我侧和腹内侧核中可见大量标记细胞。在同侧下丘脑餐侧区、背侧区、未定带和背内侧核中可见少量标记细胞。在脑干的黑质致密部、腹侧被盖区、中缝背核、导水管周灰质中也可见标记     

Retinal projection to the formatio reticularis tegmenti mesencephali in the Old World monkeys

Summary We studied the retinal projections of Old World monkeys using the anterograde transport of tritiated amino acid and wheat germ agglutinin conjugated to horseradish peroxidase. In addition to well-known retinal connections, these methods revealed that a small number of labeled retinofugal fibers might terminate in a small area of the contralateral formatio reticularis tegmenti mesencephali between the red nucleus and the substantia nigra. In the autoradiographic cases, a few labeled retinal terminals were also found in the same area on the ipsilateral side. In order to reach their terminal field, these labeled fibers appeared to leave the accessory optic tract in the vicinity of the dorsal border of the lateral terminal nucleus and run medially through the substantia nigra.     

Quantitative evaluation of crossed and uncrossed projections from basal ganglia and cerebellum to the cat thalamus

Quantitative and qualitative analysis of crossed vs uncrossed projections from the substantia nigra, entopeduncular nucleus and individual cerebellar nuclei to the thalamus was undertaken in nine adult cats using retrograde labeling with horseradish peroxidase and fluorescent dyes. The results indicate that about 90% of entopeduncular nucleus neurons and 50% of substantia nigra neurons give rise to ipsilateral projections to the thalamus whereas the contralateral component of these projections originates from about 10 and 7% neurons of entopeduncular nucleus and substantia nigra, respectively. Some of the fibers constituting the contralateral component are represented by branching axon collaterals of the neurons projecting ipsilaterally. In the basal ganglia thalamic projection, its minor component (contralateral) targets the ventral anterior and ventral medial nuclei the same as its major component (ipsilateral). However, some preferential distribution of the contralateral projections to the ventral medial nucleus appears to exist. In regard to the cerebellothalamic projections it was found that about 90% of neurons located in the dentate and interpositus nuclei and 50% of neurons in the fastigial nucleus project to the contralateral thalamus while 16% of dentate nucleus neurons and 40% of fastigial nucleus neurons give rise to the ipsilateral cerebellothalamic projections. A considerable number of ipsilateral cerebellothalamic fibers are represented by divergent axon collaterals of the same neurons projecting to the contralateral thalamus. The cerebellothalamic projections from all cerebellar nuclei including the fastigial nucleus are targeted primarily to the ventral lateral nucleus both contra- and ipsilaterally. The ventral medial nucleus receives bilateral input from the fastigial nucleus which originates from about one quarter of the thalamus projecting neurons in this nucleus. Of all other cerebellar nuclei only the dentate nucleus projects to the ventral medial nucleus and this projection is exclusively contralateral.