Origin,course and termination of dopaminergic substantia nigra neurons projecting to the amygdaloid complex in the cat

The organization of dopaminergic neurons projecting to the amygdala was examined using retrograde (horseradish peroxidase histochemistry) and anterograde ([³H]leucine autoradiography) transport methods and Falck-Hillarp histofluorescence techniques combined with microspectrofluorometry and radiofrequency lesions. Cell bodies located within the pars lateralis and pars compacta of the substantia nigra were found to project to the lateral and central amygdaloid nuclei, respectively. Both of these areas within the substantia nigra contained dopaminergic perikarya, while the central and lateral amygdaloid nuclei contained fluorescent varicosities with features indicative of dopaminergic neurons. Lesions restricted to the pars lateralis of the substantia nigra resulted in a loss of fluorescence in the lateral amygdaloid nucleus. Autoradiographic experiments revealed that the projections from the pars lateralis did not run with fibers originating from the pars compacta in the nigrostriatal tract but rather had their own course occupying a lateral position adjacent to the cerebral peduncle and joining the ventral amygdalo-fugal bundle.The data indicate that, in the cat, there are two separate dopaminergic projections to the amygdala arising from the substantia nigra.     

Afferent connections of the rat substantia nigra pars lateralis with special reference to peptide-containing neurons of the amygdalo-nigral pathway

The afferent connections of the rat substantia nigra pars lateralis have been studied using the retrograde axonal transport of fluorescent latex microspheres. The most numerous groups of retrogradely labelled nerve cell bodies were observed bilaterally in the parabrachial complex and several hypothalamic nuclei, whereas the parietal neocortex, the fundus striati, the central nucleus of the amygdala and the bed nucleus of the stria terminalis were labelled on the injected side only. The neuronal projections from the central amygdaloid nucleus to the substantia nigra pars lateralis and lateral part of the rostral pars compacta have additionally been confirmed by anterograde tracing using wheat-germ agglutinin coupled to horseradish peroxidase. The presence of some peptides in this pathway was studied by combining the use of the same retrograde tracer with immunofluorescence after intra-amygdaloid injections of colchicine. With this method, we have demonstrated that Met-enkephalin, dynorphin and neurotensin are probably utilized as neurotransmitters or co-transmitters in the neurons of the amygdalo-nigral pathway.     

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     

An autoradiographic study of efferent connections of the globus pallidus in Macaca mulatta

Summary Radioactive amino acids were injected into restricted regions of the globus pallidus of rhesus macaques to allow identification of the organization and courses of efferent pallidal projections. The previously identified projection of the internal pallidal segment (GPi) to ventral thalamic nuclei showed a topographic organization, with the predominant projection from ventral GPi being to medial and caudal ventralis anterior (VA) and lateralis (VL) and from dorsal GPi to lateral and rostral VA and VL. Pallidal efferent fibers also extended caudally and dorsally into pars caudalis of VL, but they spared the portion of pars oralis of VL shown by others to receive input from the cerebellum. In addition to centromedian labeling in all animals, the parafascicular nucleus was also labeled when isotope was injected into dorsal GPi. The medial route from GPi to the midbrain tegmentum was more substantial than has been shown before, and along this route there was an indication that some fibers terminated in the prerubral region. The projection to the pedunculopontine nucleus was extensive, and fibers continued caudally into the parabrachial nuclei.Pallidal projections to the thalamus seem to be topographically organized but spare thalamic regions that interact with area 4. Caudally directed efferent fibers follow multiple routes and extend more caudally than to the pedunculopontine nuclei.Abbreviations Cd caudate nucleus - CM centromedian nucleus - CT central tegmental tract - DPCS decussation of superior cerebellar peduncle - F fornix - FLM medial longitudinal fasciculus - GPe globus pallidus, pars externa - GPi globus pallidus, pars interna - HbL lateral habenular nucleus - HbM medial habenular nucleus - Is interstitial nucleus - LM medial lemniscus - MD dorsomedial nucleus - PbL lateral parabrachial nucleus - PbM medial parabrachial nucleus - PCS superior cerebellar peduncle - Pf parafascicular nucleus - PPN pedunculopontine nucleus - Put putamen - R reticular nucleus - Rmg red nucleus, pars magnocellularis - Rpc red nucleus, pars parvocellularis - S stria medullaris - SI substantia innominata - SNc substantia nigra, pars compacta - SNr substantia nigra, pars reticulata - St subthalamic nucleus - ST stria terminalis - THI habenulointerpeduncular tract - TM tuberomamillary nucleus - TMT mamillothalamic tract - VA nucleus ventralis anterior - VAmg nucleus ventralis anterior, pars magnocellularis - VAp nucleus ventralis anterior, pars principalis - VI nucleus ventralis intermedius - VLc nucleus ventralis lateralis, pars caudalis - VLm nucleus ventralis lateralis, pars medialis - VLo nucleus ventralis lateralis, pars oralis - VPL nucleus ventralis posterior lateralis - X area X Supported by National Institutes of Health, grant RR00166, Rehabilitation Services Administration, grant 16-P-56818, and PHS grant NS10804     

大白鼠伏核的神经联系—HRP、WGA-HRP、荧光法研究

用HRP和荧光素—伊凡氏兰(EB)、核黄(NY)对大白鼠伏核的传入性联系,用WGAHRP对其传出性联系进行了实验研究。单纯HRP(19例)和荧光素EB(6例)、NY(4例)注入或泳入伏核后所产生的逆行标记结果基本一致。在丘脑,标记细胞大量出现于丘脑的带旁核、室周核、丘脑内侧核、板内核群;其它如连合核、菱形核和丘脑后内侧核也见到一些标记细胞。在中脑、黑质密带内侧份、被盖腹侧区有大量标记细胞。在边缘系统的海马、杏仁体有大量标记细胞,而内嗅区皮质和下脚仅在一些例中有明显的标记细胞。外例隔核、苍白球、尾壳核和丘脑下部等均未见标记。将WGA-HRP注入伏核内(7例),顺行性标记纤维主要经前脑内侧束下行。标记终支最明显的部位是腹侧苍白球、终纹床核和黑质网状带;其他如外侧隔核、下丘脑外侧核、丘脑底核和Forel H_2区、未定带、黑质密带等处也可见到少量的标记终支。     

Direct projections from the globus pallidus to the midbrain and pons in the cat.

Employing the anterograde and retrograde axonal tracing techniques with Phaseolus vulgaris leucoagglutinin and cholera toxin B subunit, we demonstrated direct projections from the globus pallidus (GP) to the midbrain and pons in the cat. Cells of origin of these projections were localized in the caudal 2/3 of the GP, and their major target sites included the peripeduncular region, nucleus of the brachium of the inferior colliculus, para-lateral lemniscal zone, nucleus sagulum, external and pericentral nuclei of the inferior colliculus, and cuneiform nucleus. A combination of retrograde axonal tracing and immunohistochemistry for choline acetyltransferase revealed that GP neurons giving rise to such descending projections were primarily non-cholinergic.     

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     

Projections of the bed nucleus of the stria terminalis to the mesencephalon,pons, and medulla oblongata in the cat

Summary Injections of HRP in the nucleus raphe magnus and adjoining medial reticular formation in the cat resulted in many labeled neurons in the lateral part of the bed nucleus of the stria terminalis (BNST) but not in the medial part of this nucleus. HRP injections in the nucleus raphe pallidus and in the C2 segment of the spinal cord did not result in labeled neurons in the BNST. Injections of ³H-leucine in the BNST resulted in many labeled fibers in the brain stem. Labeled fiber bundles descended by way of the medial forebrain bundle and the central tegmental field to the lateral tegmental field of pons and medulla. Dense BNST projections could be observed to the substantia nigra pars compacta, the ventral tegmental area, the nucleus of the posterior commissure, the PAG (except its dorsolateral part), the cuneiform nucleus, the nucleus raphe dorsalis, the locus coeruleus, the nucleus subcoeruleus, the medial and lateral parabrachial nuclei, the lateral tegmental field of caudal pons and medulla and the nucleus raphe magnus and adjoining medial reticular formation. Furthermore many labeled fibers were present in the solitary nucleus, and in especially the peripheral parts of the dorsal vagal nucleus. Finally some fibers could be traced in the marginal layer of the rostral part of the caudal spinal trigeminal nucleus. These projections appear to be virtually identical to the ones derived from the medial part of the central nucleus of the amygdala (Hopkins and Holstege 1978). The possibility that the BNST and the medial and central amygdaloid nuclei must be considered as one anatomical entity is discussed.Abbreviations AA anterior amygdaloid nucleus - AC anterior commissure - ACN nucleus of the anterior commissure - ACO cortical amygdaloid nucleus - AL lateral amygdaloid nucleus - AM medial amygdaloid nucleus - APN anterior paraventricular thalamic nucleus - AQ cerebral aqueduct - BC brachium conjunctivum - BIC brachium of the inferior colliculus - BL basolateral amygdaloid nucleus - BNSTL lateral part of the bed nucleus of the stria terminalis - BNSTM medial part of the bed nucleus of the stria terminalis - BP brachium pontis - CA central nucleus of the amygdala - Cd caudate nucleus - CI inferior colliculus - CL claustrum - CN cochlear nucleus - CP posterior commissure - CR corpus restiforme - CSN superior central nucleus - CTF central tegmental field - CU cuneate nucleus - D nucleus of Darkschewitsch - EC external cuneate nucleus - F fornix - G gracile nucleus - GP globus pallidus - HL lateral habenular nucleus - IC interstitial nucleus of Cajal - ICA internal capsule - IO inferior olive - IP interpeduncular nucleus - LC locus coeruleus - LGN lateral geniculate nucleus - LP lateral posterior complex - LRN lateral reticular nucleus - MGN medial geniculate nucleus - MLF medial longitudinal fascicle - NAdg dorsal group of nucleus ambiguus - NPC nucleus of the posterior commissure - nV trigeminal nerve - nVII facial nerve - OC optic chiasm - OR optic radiation - OT optic tract - P pyramidal tract - PAG periaqueductal grey - PC cerebral peduncle - PO posterior complex of the thalamus - POA preoptic area - prV principal trigeminal nucleus - PTA pretectal area - Pu putamen - PUL pulvinar nucleus - R red nucleus - RF reticular formation - RM nucleus raphe magnus - RP nucleus raphe pallidus - RST rubrospinal tract - S solitary nucleus - SC suprachiasmatic nucleus - SCN nucleus subcoeruleus - SI substantia innominata - SM stria medullaris - SN substantia nigra - SO superior olive - SOL solitary nucleus - SON supraoptic nucleus - spV spinal trigeminal nucleus - spVcd spinal trigeminal nucleus pars caudalis - ST stria terminalis - TRF retroflex tract - VC vestibular complex - VTA ventral tegmental area of Tsai - III oculomotor nucleus - Vm motor trigeminal nucleus - VI abducens nucleus - VII facial nucleus - Xd dorsal vagal nucleus - XII hypoglossal nucleus     

Efferent fibers of the subthalamic nucleus in the monkey. A comparison of the efferent projections of the subthalamic nucleus,substantia nigra and globus pallidus

A study was made to determine the efferent projections of the subthalamic nucleus in the monkey. Because of the impossibility of producing lesions in this nucleus, not involving adjacent structures, lesions were produced by different stereotaxic approaches. Comparisons were made with degeneration resulting from localized lesions in substantia nigra and globus pallidus. Degeneration resulting from these lesions was studied in transverse and sagittal sections stained by the Nauta-Gygax method. Efferent fibers from the subthalamic nucleus pass through the internal capsule into the medial pallidal segment; a few fibers are distributed to the lateral pallidum. Some subthalamic efferent fibers pass to the contralateral globus pallidus via the dorsal supraoptic decussation, but none projection to the thalamus. Nigral efferent fibers project to parts of the ventral anterior (VAmc) and ventral lateral (VLm) thalamic nuclei. The medial pallidal segment gives fibers to: (1) ventral anterior (VA), ventral lateral (VLo) and centromedian (CM) thalamic nuclei, and (2) the pedunculopontine nucleus. The lateral pallidal segment projects exclusively to the subthalamic nucleus. Thalamic projections of the substania nigra and globus pallidus are distinctive. Subthalamic projections to the globus pallidus are more profuse than those of the substantia nigra. The following hypothesis is presented: Subthalamic dyskinesia, due to lesions in the subthalamic nucleus, is a consequence of removal of inhibitory influences acting upon the medial segment of the globus pallidus.     

Pallidotectal projection to the inferior colliculus of the rat

Summary After injection of fluorescent tracer into the inferior colliculus (IC), retrogradely labeled cells were observed not only in the temporoauditory cortex (ACx) and the substantia nigra pars lateralis, but also in the globus pallidus (GP). These labeled GP cells were localized exclusively in the caudal portion of the GP, which has been known to project to the ACx. Employing a retrograde fluorescent double labeling technique, the GP-IC neurons were found to be distributed in a separate manner from the GP-ACx neurons within the caudal GP. The present study provides further anatomical evidence that the caudal GP has a functional role in auditory processing.Abbreviations ACx temporoauditory cortex - BC Brachium conjunctivum - CP cerebral peduncle - CPu caudate putamen - DY Diamidino Yellow - EP entopeduncular nucleus - FG Fluoro-Gold - GP globus pallidus - I internal capsule - IC inferior colliculus - OT optic tract - SC superior colliculus - SN1 substantia nigra pars lateralis - T thalamus - TB True Blue - TPC nucleus tegmenti pedunculopontinus pars compacta     

A semi-quantitative atlas of 5-hydroxytryptamine-1 receptors in the primate brain

The regional distribution of 5-hydroxytryptamine-1 receptors in the primate brain was studied by semi-quantitative autoradiographic analysis of tritiated ligand binding. Areas showing the highest density of 5-hydroxytryptamine-1 receptors (greater than 200 fmol [3H]5-hydroxytryptamine bound per mg tissue), included the cerebral cortex (laminae I-II), claustrum, posterior cell group of the basal nucleus of Meynert, the infracommissural part of the globus pallidus, cortical amygdaloid nucleus, hippocampal formation (CA1-subiculum region, the anterior CA2, CA3 and CA4 regions and the molecular layer of the dentate gyrus), thalamic nuclei (parafascicular, parataenial, paraventricular and superior central lateral nuclei), substantia nigra pars reticulata, dorsal raphe nucleus and choroid plexus. The distribution of 5-hydroxytryptamine-1 receptors is compared to the distribution of both 5-hydroxytryptamine receptors and terminal fields of serotonergic projections as previously described in subprimates.     

Connectivity of striatal grafts implanted into the ibotenic acid-lesioned striatum--III. Efferent projecting graft neurons and their relation to host afferents within the grafts

Efferent projections of intrastriatally implanted striatal neurons have been studied using a combination of anterograde and retrograde axonal tracers. Adult rats subjected to a unilateral ibotenic acid lesion of the head of the caudate putamen received cell suspension grafts obtained from 14 15-day-old striatal primordia. Three and a half to 20 months after transplantation the rats received either intratransplant injections of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin or injections of fluorescent retrograde tracers. Fluoro-Gold and rhodamine-labelled latex beads, into the host globus pallidus and substantia nigra. Injections of Phaseolus vulgaris leucoagglutinin located entirely within the grafts labelled axons that ramified extensively within the tissue itself, as well as axons that extended caudally, across the graft host border, along the myelinated fascicles of the internal capsule to arborize in the medial parts of the host globus pallidus. A few axons also reached the entopeduncular nucleus. Injections of Fluoro-Gold into the host globus pallidus labelled large numbers of graft neurons, which had a prominent patchy distribution and were most abundant in the caudal portions of the grafts. Clear retrograde labelling was also seen after injection of Fluoro-Gold or rhodamine beads into the host substantia nigra, although the number of labelled graft neurons was 30-50 times lower than that seen after pallidal injections. Combined injections of Fluoro-Gold into the pallidus and rhodamine beads into the nigra showed that the vast majority of cells labelled from the nigra were also labelled by Fluoro-Gold from the pallidus. In some of the grafted and Fluoro-Gold-injected animals, the fetal donor tissue had been labelled with [3H]thymidine prior to transplantation. Many examples of neurons labelled with both [3H]thymidine and Fluoro-Gold were found after tracer injections into the host globus pallidus, and double-labelled neurons were identified also after Fluoro-Gold injections into the host substantia nigra. In several animals retrograde tracing was combined with labelling of host dopaminergic afferents (by tyrosine hydroxylase immunohistochemistry) and cortical afferents (by injections of Phaseolus vulgaris leucoagglutinin into the host frontal cortex). Comparison of adjacent sections revealed a striking overlap between the patches of Fluoro-Gold-labelled graft neurons (labelled from the host pallidum) and the dense patches of tyrosine hydroxylase-positive terminals. In addition, many of the Fluoro-Gold-labelled cell patches received a high density of cortical afferents labelled by Phaseolus vulgaris leucoagglutinin.(ABSTRACT TRUNCATED AT 400 WORDS)     

Separate neuronal populations of the rat substantia nigra pars lateralis with distinct projection sites and transmitter phenotypes.

The topographic organization of the nigral cells sending axons to the striatum, amygdala and inferior colliculus was studied in the rat substantia nigra pars lateralis by using retrograde fluorescent tracers. Nigral perikarya projecting to the inferior colliculus were located dorsolaterally within the substantia nigra pars lateralis, whereas nigral perikarya projecting to the striatum or to the amygdala were mostly situated ventromedially within the substantia nigra pars lateralis. The transmitter substances of the nigrotectal cells were examined by combining a retrograde tracing method with immunohistochemistry for tyrosine hydroxylase or glutamate decarboxylase. Nigral neurons projecting to the inferior colliculus lacked tyrosine hydroxylase immunoreactivity, but exhibited immunoreactivity for glutamate decarboxylase. The substantia nigra pars lateralis is made up of different neuronal populations: one projecting to the inferior colliculus and another directed to the striatum and amygdala. The pars lateralis pathway to the inferior colliculus utilized GABA as a neurotransmitter, whereas the previously characterized nigral cells projecting to the striatum and superior colliculus use GABA and dopamine as neurotransmitters.     

Differential connections of caudate nucleus and putamen in the squirrel monkey (Saimiri sciureus)

The organization of the subcortical connections of caudate nucleus and putamen in the squirrel monkey was studied using horseradish peroxidase conjugated to wheat germ agglutinin as anterograde and retrograde neuronal tracer. The tracer was injected in similar quantities in the putamen on the left side and in the caudate nucleus on the right side in 10 monkeys, and its presence was revealed by means of the tetramethylbenzidine method. The study of anterogradely labeled fibers visualized after such injections shows that putaminofugal fibers terminate massively in the ventral two-thirds of the globus pallidus, where they display a band-like arrangement, and much less abundantly in the caudal third of the substantia nigra. In contrast, caudatofugal fibers occupy only the dorsal third of globus pallidus but arborize profusely in the rostral two-thirds of substantia nigra. In the pars reticulata of the substantia nigra the caudatonigral fibers form a highly complex network composed of fiber trabeculae while the putaminonigral fibers occur as more discrete fascicles confined to the dorsolateral region of the structure. In the pars compacta of the substantia nigra the retrogradely labeled cells occur in the form of clusters that are closely intermingled with clusters of unlabeled neurons. The labeled-cell clusters are particularly dense on the putamen-injected side and more loosely organized on the caudate-injected side. On both sides, however, the striatonigral fibers that reach the substantia nigra pars compacta can be seen to terminate almost exclusively upon clusters composed of retrogradely labeled cells, suggesting the existence of a precise reciprocal link between nigral and striatal neuronal aggregates. At thalamic levels the retrogradely labeled cells are distributed according to a strikingly asymmetric pattern. For instance, a prominent labeling of neurons in the central superior lateral nucleus is seen only on the caudate-injected side. Furthermore, in the centromedian/parafascicular complex retrograde cell labeling is seen exclusively in parafascicular nucleus on the caudate-injected side and only in the centromedian nucleus, except its lateralmost portion, on the putamen-injected side. Control experiments involving injection of the tracer in cerebral cortex overlying the striatum reveal that the neurons in the lateral segment of the centromedian, which do not project to striatum, are in fact reciprocally connected with the cerebral cortex. In addition, our data show that some of the so-called "specific" thalamic nuclei contribute significantly to the thalamostriatal projection in monkey.(ABSTRACT TRUNCATED AT 400 WORDS)     

Projections of the substantia nigra, ventral tegmental area and amygdala to the pallidum in dog brain

Using the method based on HRP retrograde axonal transport organization of projections of substantia nigra, tegmental ventral field and amygdala on pallidum was studied. Neuronal fibres from all dopaminergic portions of substantia nigra and tegmental ventral field were found to project on both structures of dog dorsal pallidum (globus pallidus and entopeduncular nucleus). Ventral pallidum receives projectional axons only from neurons of basal nucleus of amygdala and tegmental ventral field.     

黄喉鹀耳蜗核的传出投射

用HRP顺行追踪方法,研究黄喉鵐(emberiza elegans)的两对耳蜗核,即角状核和巨细胞核的传出投射.将HRP注入角状核,在双侧上橄榄核,对侧外侧丘系核腹侧部,外侧丘系腹核及中脑背外侧核的背侧1/4的区域见到顺行标记纤维或终末.将HRP注入巨细胞核,标记纤维或终末分布于双侧层状核;标记细胞分布于同侧上橄榄核.结果表明:角状核投射至双侧上橄榄核,对侧外侧丘系核腹侧部,外侧丘系腹核及中脑背外侧核的背侧部.巨细胞核投射至双侧层状核.此外,巨细胞核接受同侧上橄榄核的传人,它可能是一条听觉的反馈回路.     

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.     

Amygdaloid projections to the mesencephalon,pons and medulla oblongata in the cat

Summary Amygdalotegmental projections were studied in 26 cats after injections of horseradish peroxidase (HRP) in the diencephalon, midbrain and lower brain stem and in 6 cats after injection of ³H-leucine in the amygdala. Following HRP injections in the posterior hypothalamus, periaqueductal gray (PAG) and tegmentum many retrogradely labeled neurons were present in the central nucleus (CE) of the amygdala, primarily ipsilaterally. Injections of HRP in the posterior hypothalamus and mesencephalon also resulted in the labeling of neurons in the basal nucleus, pars magnocellularis.Following ³H-leucine injections in CE and adjacent structures autoradiographically labeled fibers were present in the stria terminalis and ventral amygdalofugal pathways. In the mesencephalon heavily labeled fiber bundles were located lateral to the red nucleus. Labeled fibers and terminals were distributed to the mesencephalic reticular formation, substantia nigra, ventral tegmental area and PAG. In the pontine and medullary tegmentum the bulk of passing fibers was located laterally in the reticular formation. Many labeled fibers and terminals were distributed to the parabrachial nuclei, locus coeruleus, nucleus subcoeruleus and lateral tegmental fields. Many terminals were also present in the solitary nucleus and dorsal motor nucleus of the vagus nerve.The location of the cells of origin and the distribution of the terminals of the amygdalotegmental projection suggest that this pathway plays an important role in the integration of somatic and autonomic responses associated with affective defense.Abbreviations A nucleus ambiguus - AL lateral amygdaloid nucleus - AQ cerebral aqueduct - BC brachium conjunctivum - BL basal amygdaloid nucleus, pars magnocellularis - BM basal amygdaloid nucleus, pars parvocellularis - BP brachium pontis - CE central amygdaloid nucleus - CI internal capsule - CN cochlear nucleus - CO cortical amygdaloid nucleus - CP cerebral peduncle - DCN dorsal column nuclei - DMV dorsal motor nucleus of the vagus nerve - E entopeduncular nucleus - F fornix - FLA longitudinal association bundle - GP globus pallidus - H hippocampal formation - 1C inferior colliculus - INJ injection site - LC locus coeruleus - IO inferior olive - LG lateral geniculate nucleus - LRN lateral reticular nucleus - LT lateral tegmental field - M medial amygdaloid nucleus - MB mammilary body - MG medial geniculate nucleus - ML medial lemniscus - MT medial tegmental field - MV motor nucleus of the trigeminus - OC optic chiasm - OT optic tract - P putamen - PAG periaqueductal gray - PB parabrachial nuclei - PC posterior commissure - PH posterior hypothalamus - PT pyramidal tract - PV principal sensory nucleus of the trigeminus - PYR pyriform cortex - R red nucleus - RF reticular formation - S solitary nucleus - SC nucleus subcoeruleus - SN substantia nigra - SO superior olive - SOL solitary nucleus - SPV spinal trigeminal complex - ST stria terminalis - VC vestibular complex - VTA ventral tegmental area - VII facial nucleus - XII hypoglossal nucleus     

A horseradish peroxidase study of afferent connections of the globus pallidus in Macaca mulatta

Summary The high tonic discharge rates of globus pallidus neurons in awake monkeys suggest that these neurons may receive some potent excitatory input. Because most current electrophysiological evidence suggests that the major described pallidal afferent systems from the neostriatum are primarily inhibitory, we used retrograde transport of horseradish peroxidase (HRP) to identify possible additional sources of pallidal afferent fibers. The appropriate location was determined before HRP injection by mapping the characteristic high frequency discharge of single pallidal units in awake animals. In animals with injections confined to the internal pallidal segment, retrograde label was seen in neurons of the pedunculopontine nucleus, dorsal raphe nucleus, substantia nigra, caudate, putamen, subthalamic nucleus, parafascicular nucleus, zona incerta, medial and lateral subthalamic tegmentum, parabrachial nuclei, and locus coeruleus. An injection involving the external pallidal segment and the putamen as well resulted in additional labeling of cells in centromedian nucleus, pulvinar, and the ventromedial thalamus.Abbreviations AC anterior commissure - CG central grey - CM centromedian nucleus - CN caudate nucleus - DM dorsomedial nucleus - DR dorsal raphe nucleus - DSCP decussation of superior cerebellar peduncle - GPe globus pallidus, external segment - GPi globus pallidus, internal segment - LC locus coeruleus - LL lateral lemniscus - MG medial geniculate nucleus - ML medial lemniscus - NVI abducens nucleus - OT optic tract - Pbl lateral parabrachial nucleus - Pbm medial parabrachial nucleus - Pf parafascicular nucleus - PPN pedunculopontine nucleus - PuO oral pulvinar nucleus - RN red nucleus - SCP superior cerebellar peduncle - SI substantia innominata - SNc substantia nigra, pars compacta - SNr substantia nigra, pars reticulata - STN subthalamic nucleus - TMT mamillothalamic tract - VA ventral anterior nucleus - VLc ventral lateral nucleus, pars caudalis - VLm ventral lateral nucleus, pars medialis - VLo ventral lateral nucleus, pars oralis - VPI ventral posterior inferior nucleus - VPM ventral posterior medial nucleus - VPLc ventral posterior lateral nucleus, pars caudalis - ZI zona incerta     

Afferent connections of the interstitial nucleus of the posterior limb of the anterior commissure and adjacent amygdalostriatal transition area in the rat

The interstitial nucleus of the posterior limb of the anterior commissure is, like the striatum, very rich in tyrosine hydroxylase and acetylcholinesterase, but on the basis of most other neurochemical criteria displays features that are typical of the extended amygdala (Alheid, de Olmos and Beltramino, 1995). Its afferent connections were examined in the rat with retrograde (cholera toxin B subunit) and anterograde (Phaseolus vulgaris leucoagglutinin) tracers and compared to those of the neighboring amygdalostriatal transition area and central amygdaloid nucleus. Deposits of cholera toxin B subunit in the interstitial nucleus of the posterior limb of the anterior commissure result in retrograde labeling that is similar to that seen after cholera toxin B subunit injections in the central amygdaloid nucleus. Retrogradely labeled cells are found in insular, infralimbic, prelimbic, piriform, amygdalopiriform transition, entorhinal and perirhinal cortices, as well as in temporal field CA1 of Ammon horn and ventral subiculum, amygdala (nucleus of the lateral olfactory tract, anterior amygdaloid area, anterior cortical, posterolateral cortical, anterior and posterior basomedial, intercalated cells, basolateral and lateral nuclei), and extended amygdala, primarily in its central division. The latter includes the lateral bed nucleus of the stria terminalis, dorsal portions of the sublenticular region, the lateral pocket of the supracapsular bed nucleus of the stria terminalis and the central amygdaloid nucleus. Retrogradely labeled cells are also seen in midline thalamic nuclei, lateral hypothalamus, ventral tegmental area, retrorubral field, dorsal raphe nucleus, pedunculopontine and dorsolateral tegmental nuclei, locus coeruleus and parabrachial area. The central extended amygdala, lateral hypothalamus and parabrachial area display a substantial retrograde labeling only when the injection involves districts of the interstitial nucleus of the posterior limb of the anterior commissure apposed to the pallidum, i.e. its medial part. Our anterograde results confirm that projections from the lateral bed nucleus of the stria terminalis and central amygdaloid nucleus to the interstitial nucleus of the posterior limb of the anterior commissure target its medial part. They also indicate that structures which provide major afferents to the central extended amygdala (the lateral and posterior basolateral amygdaloid nuclei and the amygdalopiriform transition area) innervate chiefly the medial part of the interstitial nucleus of the posterior limb of the anterior commissure and, to a much lesser degree, its lateral part. The piriform cortex, which has well-acknowledged projections to the ventral striatum, innervates only the rostral sector of the interstitial nucleus of the posterior limb of the anterior commissure. Taken together, these data indicate that the medial part of the interstitial nucleus of the posterior limb of the anterior commissure is closely related to the central extended amygdala. Rostral and lateral parts of the interstitial nucleus of the posterior limb of the anterior commissure, on the other hand, appear as transitional territories between the central extended amygdala and ventral striatum. The afferent connections of the zone traditionally termed amygdalostriatal transition area are in general similar to those of the caudate-putamen, which does not receive projections from the central extended amygdala. After cholera toxin B subunit injections in the caudoventral globus pallidus, a dense retrograde labeling is observed in the amygdalostriatal transition area and overlying striatum, but not in the interstitial nucleus of the posterior limb of the anterior commissure. Our results suggest that the interstitial nucleus of the posterior limb of the anterior commissure and the amygdalostriatal transition area are engaged in distinct forebrain circuits; the former is a dopamine-rich territory intimately related to the central ext