Organization and efferent projections of nucleus tegmenti pedunculopontinus pars compacta with special reference to its cholinergic aspects

In an attempt to evaluate the cellular organization and efferent projections of the nucleus tegmenti pedunculopontinus pars compacta, several experiments were performed in the rat. From measurements of neurons in the nucleus tegmenti pedunculopontinus pars compacta in Nissl-stained sections, the nucleus was observed to contain many large neurons which made it possible to demarcate this nucleus from surrounding pontomesencephalic reticular formation. Two other neuronal populations, medium and small neurons, were also seen in the nucleus tegmenti pedunculopontinus pars compacta. Detailed measurements showed that 90% by volume of all neurons in the nucleus tegmenti pedunculopontinus pars compacta were large and medium-sized neurons. After injections of [ ³H]leucine into the nucleus tegmenti pedunculopontinus pars compacta, transported label was observed in dorsally and ventrally coursing ascending fibers. The dorsally coursing fibers entered the centrolateral nucleus and centre median-parafascicular complex of the thalamus. The ventrally coursing fibers produced accumulation of silver grains in the ventral tegmental area, substantia nigra pars compacta, subthalamic nucleus, zona incerta and lateral hypothalamus. Crossed fibers of the nucleus tegmenti pedunculopontinus pars compacta were observed sparsely at the levels of the thalamus and posterior commissure, and to a greater degree through the supraoptic commissure of Meynert. Much less anterograde labeling was seen in the equivalent terminal sites on the contralateral side of the brain. By electron microscopic autoradiography major terminal sites of axons of the nucleus tegmenti pedunculopontinus pars compacta were examined in rats injected with [ ³H]leucine in the nucleus tegmenti pedunculopontinus pars compacta and later injected with horseradish peroxidase in the striatum and pallidum. Statistical data showed preferential radiolabeling of terminals forming asymmetrical synaptic contact with dendrites in the centrolateral nucleus, centre median-parafascicular complex and subthalamic nucleus. Apparent terminations in the substantia nigra pars compacta proposed in earlier studies and shown in the present light microscopic autoradiograms were not supported by this ultrastructural analysis. Several radiolabeled terminals of the asymmetrical type contacting horseradish peroxidase labeled dendrites in the thalamus confirmed direct input from the nucleus tegmenti pedunculopontinus pars compacta to the thalamostriate projection neurons. [ ³H]choline injections into the thalamus and subthalamic nucleus produced retrograde perikaryal labeling of large neurons in the nucleus tegmenti pedunculopontinus pars compacta. These neurons were unlabeled after [ ³H]choline injections in the substantia nigra. Other findings suggested retrograde transport of [ ³H]choline through cholinergic terminals as well as cholinergic fibers of passage. These data suggested a selective uptake mechanism for cholinergic fibers of passage.The results emphasize the cholinergic nature of the nucleus tegmenti pedunculopontinus pars compacta innervation of the thalamus and subthalamic nucleus. Large neurons in the nucleus tegmenti pedunculopontinus pars compacta seem responsible for this cholinergic innervation and probably provide the axon terminals making asymmetrical synapses in the thalamus and subthalamic nucleus as described above. In addition, large neurons as well as medium and small ones in the nucleus tegmenti pedunculopontinus pars compacta whose transmitters and exact destinations remain unknown send a number of axons through the supraoptic commissure of Meynert to innervate the contralateral subthalamic nucleus.     

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.     

Pyramidal input to the basal ganglia in the cat

Summary In cats with mesencephalic decerebration sparing the cerebral peduncles and ablation of sensorimotor cortex, changes in firing of single neurons of caudate nucleus (CD), putamen (PU), globus pallidus (GP) and entopeduncular nucleus (EN) were studied following stimulation of the ipsilateral medullary pyramidal tract (MPT). Cells in CD and PU were not extensively influenced by impulses backfired from MPT (14.7% and 18.7%, respectively). Conversely, a larger number of GP cells (28.1%) and especially EN cells (46.9%) exhibited pronounced changes in their firing following MPT stimulation. The MPT-induced effects on CD and PU were either inhibition or excitations, the latter appearing at latencies greater than 11 ms. The responses observed in GP and EN cells were most frequently excitations, some of which appeared with latencies below 5 ms.     

Cholinergic and non-cholinergic projections from the canine pontomesencephalic tegmentum (Ch5 area) to the caudal intralaminar thalamic nuclei

Summary The distribution and morphology of cholinergic and non-cholinergic neurons projecting to the caudal intralaminar thalamic nuclei from the Ch5 area in the dog were examined using a technique combining horseradish peroxidase (HRP) retrograde labeling with choline acetyltransferase (ChAT) immunocytochemistry. After processing for ChAT, cholinergic neurons were found primarily within the nucleus tegmenti pedunculopontinus (PPN) and the central tegmental tract (ctt). ChAT positive neurons were also located in the nucleus cuneiformis and among the fibers of the lateral lemniscus and medial longitudinal fasciculus. On the basis of immunocytochemical and cytoarchitectonic data, PPN was divided into two distinct cell groups — a compact cell group located dorsolateral to the brachium conjunctivum and a diffuse cell group intermingled among the fibers of the brachium conjunctivum. Tissue processed for WGA-HRP and ChAT following injections of lectin-conjugated horseradish peroxidase into either the centrum medianum (CM) or parafascicular (Pf) nucleus resulted in double labeled cholinergic projection neurons in both PPN and ctt. Injections which involved CM and the caudal part of the central lateral thalamic nucleus (CL) resulted in more retrogradely labeled neurons than did those injections involving Pf. Injections of CM and CL also resulted in more double labeled cells in the dorsolateral compact portion of PPN than did injections confined to Pf. In all cases a small number of cholinergic neurons located in the contralateral PPN were retrogradely labeled as well. A substantial number of retrogradely labeled neurons were not ChAT positive, and in some cases, comprised up to 27% of the total population of projection neurons. Measurements of cell soma areas indicated that cells comprising the general cholinergic population were mostly medium (300–600 m²) or large (>600 m²) in size. The majority of cholinergic projection neurons fell within the medium size category while the non-cholinergic projection neurons were significantly smaller than their cholinergic counterparts. The results of this study suggest that in the dog, Ch5 cholinergic neurons which project to the caudal intralaminar thalamic nuclei are medium in size and are located primarily within PPN and ctt. In addition, a parallel projection to the caudal intralaminar nuclei exists which originates from smaller, non-cholinergic neurons in these same regions. Based on the results of this study, it appears that cholinergic projections to intralaminar thalamic nuclei which in turn project to the neostriatum may be one of the pathways over which PPN can affect basal ganglia activity.     

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     

The role of the subthalamic nucleus in the response of globus pallidus neurons to stimulation of the prelimbic and agranular frontal cortices in rats

Summary We investigated how the cerebral cortex can influence the globus pallidus by two routes: the larger, net inhibitory route through the neostriatum and the separate, smaller, net excitatory route through the subthalamic nucleus. Stimulation (0.3 and 0.7 mA) of two regions of frontal agranular (motor) cortex and of the medial orbitofrontal cortex centered in the prelimbic cortex typically elicited one or more of the following extracellularly recorded responses in over 50% of tested cells: an initial excitation (approximately 6 ms latency), a short inhibition (15 ms latency) and a late excitation (29 ms latency). Some other cells responded with an excitatory response only (18 ms latency). The excitatory responses largely arise from the subthalamic route. Kainic acid or electrolytic lesion of the subthalamic nucleus eliminated most excitatory responses and greatly prolonged the duration (16 vs 50 ms) of the inhibition. Subthalamic neurons typically showed one or more of the following responses to cortical stimulation: an early excitatory response (4 ms latency), an inhibitory period (9 ms) and a late excitatory response (16 ms). The early response was seen after motor cortex but not prelimbic stimulation. The timing of the globus pallidus and subthalamic responses suggest the operation of a reciprocal inhibitory/excitatory pathway. Two reciprocal interactions were indicated. First, pallidal inhibition may disinhibit the subthalamus and, via a feedback pathway onto the same pallidal cells, act to terminate the neostriatal-induced inhibition. Second, there may be a feedforward pathway from pallidal cells to subthalamic neurons to a different group of pallidal cells. This pathway could act to suppress competing responses. Thus the subthalamus may have three actions: 1) an early direct cortical and 2,3) later reciprocal feedforward and feedback excitatory antagonism of the neostriatal mediated inhibition of globus pallidus.     

Auditory cortical field projections to the basal ganglia of the cat

Projections to the basal ganglia from four auditory cortical fields in the cat were studied by combining microelectrode-mapping of the neurons' best frequencies with autoradiographic and histochemical tract-tracing techniques. Each auditory field is a source of projections to the homolateral basal ganglia. The distribution of labeling within the basal ganglia is related to the cortical field in which the injection site is located. The dorsal portion of the putamen and adjacent caudate nucleus are connected with cortical fields situated anteriorly and dorsally, while the ventral portion of the putamen and adjacent lateral amygdaloid nucleus are related to auditory fields situated posteriorly and ventrally. Injections of two different tracers into different best-frequency loci of one cortical field provided evidence that low best-frequency neurons project medially within the basal ganglia while high best-frequency neurons project more laterally.We concluded that there was a basic similarity among patterns of terminations in the basal ganglia from axons that originate in different auditory cortical fields. When the source of a projection was confined to a restricted portion of an auditory cortical field, labeling appeared as dense patches of silver grains separated from each other by areas of less dense labeling. Often, these patches were distributed within a sheet of tissue, elongated both dorsoventrally and anteroposteriorly. Loci having the same best-frequency representation, but situated in different auditory cortical fields, project upon overlapping but not coextensive portions of a single sheet of tissue. Thus the projections from geographically distant cortical loci possessing similar best-frequency representations are notably distinguished on a topographic basis. By comparison, two adjacent sheets of tissue were labeled when two injections were made into the low best-frequency and high best-frequency representations of the same auditory field. Doubleinjection, double-tracer experiments revealed that adjacent sheets of tissue received projections from different best-frequency loci. These observations suggested a degree of tonotopic organization to this projection system which was equipoise to the evidence obtained for a topographic organization.     

Topographic organization of projections from the amygdala to the hypothalamus of the rat

Afferent fibers from the amygdala to subdivisions of lateral, ventromedial and dorsomedial hypothalamic nuclei were investigated in rat by retrograde transport of horseradish peroxidase. Small (intranuclear size) peroxidase deposits were placed in hypothalamic nuclei by iontophoresis of a tracer solution containing poly-L-alpha-ornithine which greatly limited diffusion. The medial, central and amygdalo-hippocampal nuclei of the amygdala were found to be the major donors of amygdaloid afferent fibers to the hypothalamus, but there was also substantial labeling of somata in cortical, basomedial, basolateral and lateral amygdaloid nuclei and the intra-amygdaloid bed nucleus of the stria terminalis. No fibers projected from the posterior cortical nucleus of the amygdala to the hypothalamus. Most amygdaloid projections to the lateral hypothalamic area originated in the anterior half of the amygdala, while projections to the ventromedial hypothalamic nucleus arose along the entire length of the amygdala except the posterior cortical nucleus. The amygdalo-hippocampal area projects to the medial hypothalamus. Other amygdaloid nuclei project to both the medial and lateral hypothalamic nuclei. These topographic organizations of amygdaloid afferent fibers to various subdivisions of the hypothalamic nuclei are discussed and compared with other anatomical studies on these connections.     

Direct projections from thalamic intralaminar nuclei to extra-striate visual cortex in the cat traced with Horseradish peroxidase

Summary Thalamic projections to the visual cortex were investigated using the Horseradish peroxidase tracing technique. Besides confirmation of a distinct origin of thalamic projections to striate and extra-striate visual cortex, afferents of the intralaminar nuclei (ILN) to visual cortex were demonstrated. These projections of ILN were shown to be specific in that they terminate in areas 18, 19 and Clare Bishop but not area 17. The coupling of these intralaminar projections on to the extra-striate visual system is considered with respect to orientation of gaze.     

Topographical arrangement of thalamocortical neurons in the centrolateral nucleus (CL) of the cat,with special reference to a spino-thalamo-motor cortical path through the CL

Summary In the centrolateral nucleus of the thalamus (CL) in the cat, a topographical arrangement of the thalamocortical projection neurons was demonstrated by utilizing retrograde axonal transport of horseradish peroxidase (HRP). Following injections of HRP into the medial or lateral areas of the anterior sigmoid gyrus (ASG), HRP-labeled neurons were located medially or laterally in the caudal levels of the CL, respectively; neurons in the central areas of the CL were labeled after injections of HRP into the rostral areas of the middle suprasylvian or the lateral gyrus.It was also shown by means of the combined HRP and Fink-Heimer method (Blomqvist and Westman, 1975) that the spinothalamic fibers terminated around CL neurons which were labeled with HRP injected into the lateral areas of the ASG. Hence, the caudolateral aspects of the CL were considered to represent a relay of the spino-thalamo-motor cortical paths.     

A horseradish peroxidase study of the projections from the lateral reticular nucleus to the cerebellum in the rat

Summary The projection from the lateral reticular nucleus (LRN) to the cerebellar cortex was studied in the rat by utilizing the retrograde transport of horseradish peroxidase (HRP). In order to study the topographic features of this projection, small amounts of HRP were injected into various sites in the cerebellar cortex. The results demonstrated that the caudal lobules of the anterior lobe vermis tend to receive afferents from the medial LRN and the rostral lobules of the vermis receive afferents from more laterally situated cells. Lobules IV and V receive inputs primarily from the magnocellular division of the LRN of both the ventromedial and dorsolateral parts of the LRN, while lobules II and III receive inputs mainly from cells which lie in the border area between the parvocellular and magnocellular division of the ventromedial part. Following injections within various areas of the posterior lobe vermis, the results indicated that lobule VIII receives the most abundant projection from the LRN and that the cells of origin are present within the parvocellular and the adjacent part of the magnocellular division throughout the rostrocaudal extent of the LRN. Following injections within lobules VI and VII, few labelled cells were found and they tended to lie within the rostral two-thirds of the magnocellular division. Little or no projection from the LRN to lobule IX was evident. The hemispheres were found to receive a modest projection from the dorsal aspect of the LRN. The projection to lobulus simplex originates mainly from the caudal two-thirds of the magnocellular division, while the projection to the ansiform and paramedian lobules originates mainly from the dorsal aspect of the rostral two-thirds of the magnocellular division. Finally, there appears to be extensive overlapping of the orgins of all three projections to the cerebellar cortex studied, and this occurs within the central area of the magnocellular division throughout the rostrocaudal extent of the LRN.     

GABAergic projections from the thalamic reticular nucleus to the anteroventral and anterodorsal thalamic nuclei of the rat

We have studied GABAergic projections from the thalamic reticular nucleus to the anterior thalamic nuclei of the rat by combining retrograde labelling with horseradish peroxidase and GABA-immunohistochentistry. Small iontophoretic injections of the tracer into subnuclei of the anterior thalamic nuclear complex resulted in retrograde labelling of cells in the rostrodorsal pole of the ipsilateral thalamic reticular nucleus. All of these cells were also GABA-positive. The projections were topographically organized. Neurons located in the most dorsal part of the rostral reticular nucleus projected to the dorsal half of both the posterior subdivision and the medial subdivision of the anteroventral thalamic nucleus, and to the rostral portion of the anterodorsal thalamic nucleus. Immediately ventral to this group of neurons, but still within the dorsal portion of the reticular nucleus, a second group of neurons, extending from the dorsolateral to the dorsomedial edge of the nucleus, projected to the ventral parts of the posterior and medial subdivisions of the anteroventral nucleus. Following injection of tracer into the dorsal part of the rostral anteroventral nucleus, retrograde labelled GABA-containing cell bodies were also found in the ipsilateral anterodorsal nucleus.     

Topographical projections from the cerebral cortex to the nucleus of the solitary tract in the cat

Summary The distribution of cerebral cortical neurons sending projection fibers to the nucleus of the solitary tract (NST), and the topographical distribution of axon terminals of cortico-NST fibers within the NST were examined in the cat by two sets of experiments with horseradish peroxidase (HRP) and HRP conjugated with wheat germ agglutinin (WGA-HRP). First, HRP was injected into the NST. In the cerebral cortex of these cats, neuronal cell bodies were labeled retrogradely in the deep pyramidal cell layer (layer V): After HRP injection centered on the rostral or middle part of the NST, HRP-labeled neuronal cell bodies were distributed mainly in the orbital gyrus and caudal part of the infralimbic cortex, and additionally in the rostral part of the anterior sylvian gyrus. After HRP injection centered on the caudal part of the NST, labeled neuronal cell bodies were seen mainly in the caudoventral part of the infralimbic cortex, and additionally in the orbital gyrus, posterior sigmoid gyrus and rostral part of the anterior sylvian gyrus. The labeling in the infralimbic cortex, orbital gyrus and anterior sylvian gyrus was bilateral with a predominantly ipsilateral distribution, while that in the posterior sigmoid gyrus was bilateral with a clear-cut contralateral dominance. In the second set of experiments, WGA-HRP was injected into the cerebral cortical regions where neuronal cell bodies had been retrogradely labeled with HRP injected into the NST: After WGA-HRP injection into the orbital gyrus, presumed axon terminals in the NST were labeled in the rostral two thirds of the nucleus bilaterally with an ipsilateral predominance. After WGA-HRP injection into the rostral part of the anterior sylvian gyrus, a moderate number of presumed axon terminals were labeled throughout the whole rostrocaudal extent of the NST bilaterally with a slight ipsilateral dominance. After WGA-HRP injection into the middle and caudal parts of the anterior sylvian gyrus, no labeling was found in the NST. After WGA-HRP injection into the caudal part of the infralimbic cortex, presumed terminal labeling in the NST was seen throughout the whole rostrocaudal extent of the nucleus bilaterally with a dominant ipsilateral distribution. After WGA-HRP injection into the posterior sigmoid gyrus, however, no terminal labeling was found in the NST. The results indicate that cortico-NST fibers from the orbital gyrus terminate in the rostral two thirds of the NST, while those from the infralimbic cortex and the rostral part of the anterior sylvian gyrus project to the whole rostrocaudal extent of the NST.     

The distribution of cholinergic perikarya with respect to enkephalin-rich patches in the caudate nucleus of the adult cat

The distribution of cholinergic interneurons with respect to enkephalin-rich patches in the caudate nucleus of the cat was examined using both computer-assisted 3-D reconstruction and immunocytochemical techniques. Examination of the 3-D distribution of perikarya staining for choline acetyltransferase (ChAT) revealed that these cells were not evenly distributed within the caudate nucleus but exhibited areas of increased and decreased density. Comparison of the 3-D distribution of cholinergic perikarya to that of the enkephalin-rich patches indicated that areas of increased ChAT+ cell density often corresponded to the positions of enkephalin-rich patches within the dorsal-lateral caudate nucleus. At more ventral regions, there was no clear correspondence between areas of increased ChAT+ cell density and enkephalin-rich patches. In agreement with these observations, a quantitative analysis of sections double-labeled for ChAT and enkephalin revealed that the density of cholinergic neurons within enkephalin-rich patches was twice that in the surrounding tissue in the dorsal region of the caudate nucleus. In contrast at more ventral levels, the difference in the density of ChAT+ cells in enkephalin-rich patches did not significantly differ from that in the surrounding striatal tissue. Both the results of the 3-D and the double-labeling analysis suggest that cholinergic neurons are not evenly distributed within the caudate nucleus of the cat but form loose clusters which are associated dorsally with the enkephalin-rich patches. These results also provide further evidence of heterogeneity within the striosomal compartment in the cat.     

Afferent fiber connections from lower brain stem to hypothalamus studied by the horseradish peroxidase method with special reference to noradrenaline innervation

Summary Attempts were made to determine the afferent projections to the anterior hypothalamus including the preoptic area from the lower brain stem by means of the horseradish peroxidase method combined with monoamine oxidase staining to identify noradrenaline (NA) neurons. In addition to this technique, a histofluorescence analysis was performed. NA fibers in the medial part of the anterior hypothalamus were mainly supplied by A1 and A2 NA neuron groups, while the lateral part and periventricular zone received NA terminals from both pontine and medulla oblongata NA neuron groups. Furthermore, the present study indicated that there were direct projections to the anterior hypothalamus from non-noradrenergic neurons in the lower brain stem: nuclei raphe dorsalis, centralis superior, cells in the mesencephalic and pontine central gray matter, nuclei parabrachialis lateralis and medialis, cells around fasciculus longitudinalis medialis.Abbreviations CA Commissura anterior - CO Chiasma opticum - DP Decussatio pyramidum - DPCS Decussatio pedunculorum cerebellarium superiorum - F Columna fornicis - FLM Fasciculus longitudinalis medialis - FMT Fasciculus mamillothalamicus - GCM Griseum centrale mesencephali - GCP Griseum centrale pontis - LL Lemniscus lateralis - LM Lemniscus medialis - PCM Pedunculus cerebellaris medius - PCS Pedunculus cerebellaris superior - TO Tractus opticus - TS Tractus solitarius - TVme Tractus mesencephalicus nervi trigemini - V Ventriculus tertius - VTS Tractus spinalis nervi trigemini - am nucleus ambiguus - B Barrington nucleus - com nucleus commissuralis - cp nucleus caudatus putamen - cs nucleus centralis superior - ct nucleus corporis trapezoidei - cu nucleus cuneatus - dX nucleus dorsalis nervi vagi - Gd nucleus tegmentalis dorsalis (von Gudden) - gr nucleus gracilis - Gv nucleus tegmentalis ventralis (von Gudden) - ha nucleus hypothalamicus anterior - hl nucleus hypothalamicus lateralis - hpe nucleus periventricularis (hypothalami) - hvm nucleus ventromedialis hypothalami - lc nucleus locus coeruleus - oi nucleus olivaris inferior - p nucleus pontis - pa nucleus paraventricularis - pbl nucleus parabrachialis lateralis - pbm nucleus parabrachialis medialis - ph nucleus praepositus hypoglossi - pol nucleus preopticus lateralis - pom nucleus preopticus medialis - pop nucleus preopticus periventricularis - rd nucleus raphe dorsalis - re nucleus reuniens - rl nucleus reticularis lateralis - rm nucleus raphe magnus - ro nucleus raphe obscrus - sc nucleus suprachiasmaticus - so nucleus supraopticus - st nucleus interstitialis striae terminalis - td nucleus tractus diagonalis (Broca) - ts nucleus tractus solitarii - Vme nucleus mesencephalicus nervi trigemini - Vmo nucleus motorius nervi trigemini - Vts nucleus tractus spinalis nervi trigemini - XII nucleus nervi hypoglossi     

Cerebellar afferent projections from the vestibular nuclei in the cat: An experimental study with the method of retrograde axonal transport of horseradish peroxidase

Summary Details of cerebellar afferent projections from the vestibular nuclei were investigated by the method of retrograde axonal transport of horseradish peroxidase (HRP) in the cat. The distribution of labeled cells in the vestibular nuclei following HRP injections in various parts of the cerebellum indicates that vestibular neurons in the medial and descending nuclei and cell groups f and x project bilaterally to the entire cerebellar vermis, the flocculus, the fastigial nucleus and the anterior and posterior interpositus nuclei. In addition, labeled cells (giant, medium and small) were consistently found bilaterally in the superior and lateral vestibular nuclei following HRP injections in the nodulus, flocculus, fastigial nucleus, and following large injections in the vermis. No labeled cells were observed in cases of HRP injections in crus I and II, the paramedian lobule, paraflocculus and lateral cerebellar nuclei. The present findings indicate that secondary vestibulocerebellar fibers project to larger areas in the cerebellum and originate from more subdivisions and cell groups of the vestibular nuclear complex than previously known.List of Abbreviations B.c. superior cerebellar peduncle (brachium conjunctivum) - D descending (inferior) vestibular nucleus - f cell group f in descending vestibular nucleus - g group rich in glia cells, caudal to the medial vestibular nucleus - HIX hemispheral lobule IX - HVIIA cr. Ia, p; cr. IIa, p anterior and posterior folia of crus I and II of the ansiform lobule - HVIIB, HVIIIA, B sublobules A and B of hemispheral lobules VII and VIII - i.c. nucleus intercalatus (Staderini) - L lateral vestibular nucleus (Deiters) - l small-celled lateral group of lateral vestibular nucleus - M medial (triangular or dorsal) vestibular nucleus - N. cu. e. accessory cuneate nucleus - N. f. c. cuneate nucleus - N. mes. V mesencephalic nucleus of trigeminal nerve - N.tr. s. nucleus of solitary tract - N. VII facial nerve - pfl. d. dorsal paraflocculus - pfl. v. ventral paraflocculus - S superior vestibular nucleus (Bechterew) - Sv. cell group probably representing the nucleus supravestibularis - Tr. s. solitary tract - x small-celled group x, lateral to the descending vestibular nucleus - y small-celled groupy, lateral to the lateral vestibular nucleus (Deiters) - z cell group dorsal to the caudal part of the descending vestibular nucleus - I–VI vermian lobules I–VI - V, VI, XII cranial motor nerve nuclei - VIIA, B; VIIIA, B anterior and posterior sublobules of lobules VII and VIII - IX uvula - X nodulus; dorsal motor nucleus of vagus nerve On leave from the Laboratory of Neurobiology and Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand, under the Felllowship Program of the Norwegian Agency for International Development (NORAD)     

Anatomical evidence for the projections from the basal nucleus of the amygdala to the primary visual cortex in the cat

The amygdaloid complex receives information from all sensory systems, especially from vision. In the primate, the amygdala is reciprocally interconnected with some regions of high-order visual cortices such as TE and TEO and only projects to the primary visual cortex (V1, area 17) without direct projection from V1. However, in the cat little is known about the projection from the amygdala to the primary visual cortex. In this study, anatomical study is carried out in cats to determine whether the amygdala sends feedback projection to area 17. FlouroGold, a fluorescent dye was microinjected into area 17 in cats. In the basal nucleus in the amygdala, the retrograde labeled cells (about 30% of total number of the region of interest observed) are distributed widely in an irregular manner, neither in lamina nor in group. The results provide the first anatomical evidence of the amygdale projection to area 17 in the cat, which is a widely used animal model for vision research.     

Somatotopical organization of the projection from the nucleus interpositus anterior of the cerebellum to the red nucleus. An experimental study in the cat with silver impregnation methods

Summary Small lesions were done in various areas of the nucleus interpositus anterior (NIA) of the cerebellum, and the distribution of terminal degeneration was studied in the red nucleus with the methods of Nauta and Glees. The NIA projects to the contralateral red nucleus. Two principles of organization can be demonstrated in the projection: a caudorostral arrangement in the red nucleus corresponds to a mediolateral organization in the NIA and a mediolateral arrangement in the red nucleus corresponds to a caudorostral organization of the NIA. The latter distribution coincides with the somatotopical areas of the red nucleus defined by Pompeiano and Brodal (1957). Special attention has been paid to the questions of the subdivision of the cerebellar nuclei and of the course of the fibres issuing from the nuclei in the cerebellar hilus. The present findings on the projection of the NIA to the red nucleus have been correlated with recent anatomical and physiological data on the cerebellum and the red nucleus.Abbreviations BC brachium conjunctivum - c caudal - d dorsal - Ext extensor effects - Flex flexor effects - forel forelimb area - HB hook-bundle - Hb. P habenulo-peduncular tract - hindl hindlimb area - I lateral - m medial - NF nucleus fastigii or medialis - NIA nucleus interpositus anterior - NIP nucleus interpositus posterior - NL nucleus lateralis - r rostral - v ventral - III root fibres of the third nerve - IV fourth ventricle Fellow of the Canadian Medical Research Council.     

Ultrastructural data,with special reference to bouton/glial relationships,from the hypoglossal nucleus after a second axotomy of the hypoglossal nerve

Summary The left hypoglossal nerve of adult male albino rats was prevented from regenerating to the tongue after a distal axotomy by implanting the proximal stump into normally innervated left sternomastoid muscle. Eighty-four days after implantation, the hypoglossal nerve was transected again and its regeneration to the tongue unimpeded. From 8 to 70 days after this second axotomy the left hypoglossal nuclei were processed for quantitative ultrastructural analysis. The first aim of this study was to compare regeneration success in the hypoglossal nucleus after second axotomy with that accompanying outgrowth of the hypoglossal nerve into denervated sternomastoid muscle. During quantitative analysis a second aim developed, of elucidating bouton/glial relationships.The second axotomy induced loss and return of subsurface cisterns, dispersal and reassembly of Nissl substance, increase and decrease of microglial numbers, slight further loss and partial return of boutons with clear spherical vesicles and symmetrical synapses, slight increase and decrease of boutons with clear flat vesicles and symmetrical synapses, regrowth of retracted dendrites and restoration of their synapses, and gradual diminution of numbers of electron-dense neurones and dendrites. Astrocytes remained hypertrophied throughout.When compared with events in the hypoglossal nucleus accompanying innervation of denervated sternomastoid muscle by the hypoglossal nerve, the results suggest (1) that regeneration of the hypoglossal nerve to its own tongue muscle instead of to a foreign muscle caused no acceleration of recovery in the hypoglossal nucleus, and (2) that the microglial response is dependent on nerve integrity and not on bouton behaviour.