Noradrenaline innervation of the spinal cord studied by the horseradish peroxidase method combined with monoamine oxidase staining

Summary The origin of the spinal cord noradrenaline (NA) has been investigated by means of the horseradish peroxidase (HRP) method, combined with monoamine oxidase staining (Glenner) to identify the NA neurons. Following the injection of HRP to the various levels of rat spinal cord, cervical to sacral cord, A1–3, 5–7 NA neuron groups were labeled with HRP. They showed almost the same distribution pattern regardless of difference in the injected segment. Labeled NA neurons in A6 were concentrated in the ventral division of the locus coeruleus, which continued to the labeled NA neurons in the subcoeruleus area. The HRP positive neurons in the pons outnumbered those of the medulla oblongata. As the NA neurons described above were considered to be the source of NA in the forebrain, such as the hypothalamus and preoptic area, the possibility that the same NA neurons might innervate both the forebrain and spinal cord has been presented.     

Cortical and brain stem projections to the spinal cord of the hedgehog (Erinaceus europaeus). A horseradish peroxidase study

Summary Cortical and brain stem neurons projecting to the spinal cord in the hedgehog were studied by means of the horseradish peroxidase (HRP) tracing method. HRP injections were placed in the first cervical segments, in the cervical enlargement (C₅-T₃) and in the lumbar enlargement. Following injections in the first cervical segments and in the cervical enlargement labelled neurons were observed in the somatic motor and somatic sensory cortices, the paraventricular and the dorsomedial hypothalamic nucleus, the lateral hypothalamic area, the nuclei of field H of Forel, the red nucleus, the mesencephalic reticular formation, the deep layers of the superior colliculus, the Edinger-Westphal nucleus, the periaqueductal grey, the mesencephalic trigeminal nucleus, the loci coeruleus and subcoeruleus, the nuclei raphe dorsalis, centralis superior, raphe magnus, raphe pallidus, and raphe obscurus, the rhombencephalic reticular formation, the lateral, medial and caudal vestibular nuclei, the nucleus ambiguus, the nucleus of the solitary tract and the gracile nucleus. After HRP injections in the lumbar enlargement, labelled neurons were not found in the cortex, the dorsomedial hypothalamic nucleus, the nuclei of field H of Forel, the superior colliculus and the mesencephalic trigeminal nucleus. These results show that cortical and brain stem projection to the spinal cord are comparable to those described in other species.Abbreviations ac anterior commissure - Am nucleus ambiguus - Aq cerebral aqueduct - cc corpus callosum - Cd caudate nucleus - CE cervical enlargement - CeS nucleus centralis superior - CG periaqueductal grey - ci capsula interna - Cq cochlear nuclei - cp cerebral peduncle - Cu cuneiform nucleus - CV caudal vestibular nucleus - DM dorsomedial hypothalamic nucleus - DX dorsal motor nucleus of vagus - EC external cuneate nucleus - EW Edinger-Westphal nucleus - F nuclei of field H of Forel - G gracile nucleus - H nippocampus - IC inferior colliculus - IP interpeduncular nucleus - LC locus coeruleus - LE lumbar enlargement - LH lateral hypothalamic area - LL nucleus of lateral lemniscus - lo lateral olfactory tract - LV lateral vestibular nucleus - MC medial cuneate nucleus - MesV mesencephalic trigeminal nucleus - MG medial geniculate nucleus - MM medial mammillary nucleus - MV medial vestibular nucleus - oc optic chiasm - PH nucleus praepositus - Pn pontine nuclei - Put putamen - PV paraventricular hypothalamic nucleus - R red nucleus - Rd nucleus raphe dorsalis - RGc gigantocellular reticular nucleus - Rl lateral reticular nucleus - Rm nucleus raphe magnus - Rmes mesencephalic reticular formation - Ro nucleus raphe obscurus - Rpa nucleus raphe pallidus - Rpc caudal reticular nucleus of the pons - Rpo rostral reticular nucleus of the pons - Rv ventral reticular nucleus - s solitary tract - SC superior colliculus - SN substantia nigra - SO supraoptic nucleus - SR sulcus rhinalis - STh subthalamic nucleus - siV spinal tract of trigeminal nerve - STV nucleus of spinal tract of trigeminal nerve - subC locus subcoeruleus - SuM supramammillary nucleus - Th thalamus - TS nucleus of solitary tract - VM ventromedial hypothalamic nucleus - ZI zona incerta - 3V third ventricle - 4V fourth ventricle - IV layer IV of the cortex - V layer V of the cortex - VI layer VI of the cortex - 7 facial nucleus - 12 hypoglossal nucleus     

Afferent innervation of extraocular muscles in the rat studied by retrograde and anterograde horseradish peroxidase transport

After injection of horseradish peroxidase (HRP) into extraocular muscles of rat perikarya were labeled mainly along the medial edge of the ophthalmic subdivision of the trigeminal ganglion but not in the mesencephalic nucleus of the trigeminal nerve. Injections of HRP into the trigeminal ganglion labeled simple as well as branching and meandering free fiber endings in extraocular muscles. No evidence for muscle spindles was found, but the meandering endings may be considered as candidates for stretch receptors.     

Olivary afferents from the raphe nuclei as studied with retrograde transport of horseradish peroxidase

Summary The afferent projection to the olive from the raphe nuclei in the cat has been studied in animals where microinjections of horseradish peroxidase have been made into the inferior olive from a ventral approach. Retrogradely labelled cells were present in the three caudalmost raphe nuclei: the nucleus raphe pallidus, obscurus and magnus. The retrogradely labelled cells are of all sizes, and there appears to be a higher concentration of cells on the side ipsilateral to the injection. The observations demonstrate that all three major subdivisions of the olive — the medial accessory, the dorsal accessory and the principal olive — all receive efferent raphe fibres. No retrogradely labelled cells were present in the other raphe nuclei.The findings are discussed and related to other tracer studies dealing with olivary afferents from the raphe complex.     

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 cerebellar projection from the raphe nuclei in the cat as studied with the method of retrograde transport of horseradish peroxidase

Summary Following injections of horseradish peroxidase (HRP) in the cerebellar cortex and nuclei of the cat, the distribution of labeled cells in the raphe nuclei was mapped. The findings confirm those made previously in studies of retrograde cell degeneration following cerebellar ablations (Brodal et al., 1960a), and in addition reveal new details in the projection of the raphe nuclei onto the cerebellar cortex and nuclei.All the raphe nuclei except nucleus linearis intermedius and nucleus linearis rostralis project onto the cerebellar cortex. The nuclei raphe obscurus and pontis contribute the greatest number of afferents to the cerebellum.With the exception of lobule VI which probably is the recipient of a weak projection, all parts of the cerebellar cortex receive afferents from the raphe nuclei. The heaviest projection is to the vermis of lobules VIIA and X, and to crus II. The afferents to the cerebellar nuclei are few in number (Tables 2–6).The observations indicate that each raphe neuron probably projects to more than one terminal site in the cerebellum.The findings are discussed with reference to other efferent and afferent studies of the raphe nuclei. All these studies indicate that the raphe nuclei have widespread efferent and afferent connections, making them capable to participate in a variety of regulatory functions.List of abbreviations f.apm. Ansoparamedian fissure - f.icul. Intraculminate fissure - f.in.cr. Intercrural fissure - fl. Flocculus - f.pc. Preculminate fissure - f.pfl. parafloccular fissure - f.ppd. Prepyramidal fissure - f.pr. Fissura prima - f.prc. Precentral fissure - f.prc.a Precentral fissure a - f.p.l. Posterolateral fissure - f.p.s. Posterior superior fissure - f.sec. Fissura secunda - HII–HX Hemispheral lobules II–X - HVIIA cr.I, cr. II Crus I and II of lobule HVIIA - HVIIIA,B Sublobules A and B of lobule HVIII - Li Nucleus linearis intermedius - Lr Nucleus linearis rostralis - l.ans. Ansiform lobule - N.f. Nucleus fastigii - N.i.a. Nucleus interpositus anterior - N.i.p. Nucleus interpositus posterior - N.l. Nucleus lateralis - pfl.d. Dorsal paraflocculus - pfl.v. Ventral paraflocculus - Rd Nucleus raphe dorsalis - Rm Nucleus raphe magnus - Rob Nucleus raphe obscurus - Rpa Nucleus raphe pallidus - Rpo Nucleus raphe pontis - Sc Nucleus raphe centralis superior - s.int.cr.1 Intracrural sulcus 1 - s.int.cr.2 Intracrural sulcus 2 - I–VI Vermian lobules I–VI - VIIA,B Anterior and posterior sublobule of lobule VII - VIIIA,B Anterior and posterior sublobule of lobule VIII     

Evidence for a spinal afferent innervation of the guinea pig lower respiratory tract as studied by the horseradish peroxidase technique

The afferent innervation of the guinea pig lower respiratory tract was studied using a retrograde axonal transport technique with application of horseradish peroxidase (HRP) onto the lining respiratory epithelium. HRP-labeled cells were observed not only in the nodose ganglia but also in the jugular and upper thoracic dorsal root ganglia (mainly at the T2&T3 levels). Thus, both vagal parasympathetic and spinal sympathetic afferents seem to have peripheral branches close to or within the respiratory epithelium suggesting a dual sensory control of the airways.     

Thalamic projections to the posterior sylvian and posterior ectosylvian gyri of the sheep brain, revealed with the retrograde transport of horseradish peroxidase

Summary The auditory area of the sheep cerebral cortex was studied on the basis of its afferents from the medial geniculate nucleus, traced with the horseradish peroxidase retrograde transport method. The results show that the medial geniculate nucleus projects only to the anterior parts of the posterior ectosylvian gyrus and the posterior sylvian gyrus. A small area of the posterior ectosylvian gyrus receives afferents exclusively from the ventral part of the medial geniculate nucleus, while the anterior part of the posterior sylvian gyrus receives also afferents from the posterior nucleus of the thalamus and the pulvinar. In addition, it was found that the medial part of the medial geniculate nucleus projects in a sparse way to the auditory cortex. The middle part of the posterior ectosylvian gyrus receives afferents from the posterior nucleus of the thalamus, the suprageniculate nucleus and the pulvinar, while the posterior part of the posterior ectosylvian gyrus together with the posteriormost part of the posterior sylvian gyrus receive afferents from the pulvinar. Finally, the area located between the anterior and the posteriormost part of the posterior sylvian gyrus receives afferents from both the posterior nucleus of the thalamus and the pulvinar.Abbreviations Ad nucleus anterior dorsalis - Am nucleus anterior medialis - Av nucleus anterior ventralis - BCI nucleus of the brachium colliculi inferioris - bci brachium colliculi inferioris - Cg substantia grisea centralis - ci capsula interna - Cm nucleus centralis medialis - EC sulcus ectomarginalis - EN sulcus entomarginalis - Ep epiphysis - ES sulcus ectosylvius - fd columna fornicis descendens - FS fissura sylvia - Hl nucleus habenularis lateralis - Hm nucleus habenularis medialis - Iv nucleus interventralis - Ld nucleus lateralis dorsalis - LGN nucleus geniculatus lateralis - LGNd nucleus geniculatus lateralis, pars dorsalis - LGNv nucleus geniculatus lateralis, pars ventralis - lme lamina medullaris thalami externa - Lp nucleus lateralis posterior - Lt nucleus lateralis thalami - MA sulcus marginalis - Md nucleus medialis dorsalis - MGN nucleus geniculatus medialis - MGNd nucleus geniculatus medialis, pars dorsalis - MGNm nucleus geniculatus medialis, pars magnocellularis - MGNv nucleus geniculatus medialis, pars ventralis - MIN medial interlaminar nucleus - mt fasciculus mamillothalamicus - ml lemniscus medialis - Mv nucleus medialis ventralis - ot tractus opticus - p putamen - pc pedunculus cerebri - Pl nucleus paralemniscalis - Po nucleus posterior - Pp nucleus paraventricularis posterior - Pta nucleus praetectalis anterior - Ptp nucleus praetectalis posterior - Pul pulvinar - R nucleus ruber - rf fasciculus retroflexus - Rh nucleus rhomboidalis - RH sulcus rhinalis lateralis - Rt nucleus reticularis thalami - Sg nucleus suprageniculatus - SN substantia nigra - SP sulcus cinguli - SS sulcus suprasylvius - Sth nucleus subthalamicus - Va nucleus ventralis anterior - Vl ventrolateral nuclear complex - Vll pars lateralis of the ventrolateral nuclear complex - Vm nucleus ventralis medialis - Vp nucleus ventralis posterior - Vpl nucleus ventralis posterior, pars lateralis - Vpm nucleus ventralis posterior, pars medialis - W Wernicke's field     

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)     

Direct contacts between glossopharyngeal afferent terminals and hypoglossal motoneurons revealed by double labeling with cobaltic-lysine and horseradish peroxidase in the Japanese toad

Glossopharyngeal (IX) afferents and hypoglossal (XII) motoneurons of the Japanese toad were simultaneously labeled with cobaltic-lysine and horseradish peroxidase, respectively. Some of the terminal branches of the IX afferents had direct contacts with the dorsal dendrites, the lateral dendrites and the somata of the XII motoneurons, but not with the medial dendrites. Such direct contacts mainly occurred in the rostral region of the dorsomedial XII nucleus, where tongue-retractor motoneurons predominate, but not in the caudal region nor in the ventrolateral XII nucleus.     

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     

Non-reciprocal connections between the vestibular nuclei and the cerebellar paramedian lobule, with special reference to the climbing fiber zones: an analysis in the rabbit using the retrograde horseradish peroxidase method.

The organization of the secondary vestibular projections onto the cerebellar paramedian lobule (PML) and possible reciprocal corticovestibular connections were investigated by the retrograde horseradish (HRP) technique in the rabbit. Following injections of the tracer into the vestibular nuclear complex (VNC), an ill-defined, sagittal band composed of numerous labelled Purkinje cells was found ipsilaterally throughout the length of the lateral portion of the vermis, the ventral paraflocculus and the flocculus. However, no labelled Purkinje cells were found in the cortex of the PML. The results indicate that zone B, considered to give rise to cerebellar corticovestibular projections, is not present in the rabbit PML. After injections of HRP into the PML, the retrograde labelling pattern in the VNC was analyzed, in relation to the climbing fiber zones identified by retrograde labelling in the inferior olive. No clear-cut correspondence could be found between the vestibular subdivisions and climbing fiber zones in the PML, except that only the interstitial nucleus of the vestibular nerve projects into zone D1 in sublobules e and d. There were no vestibular projections to zone D2. The only salient feature was that cells projecting onto zones C2, C1 and C3 of the PML were arranged rostrocaudally in the inferior vestibular nucleus and the caudal portion of the medial vestibular nucleus. In addition, a topical relationship was found between parts of the VNC and sublobules of the PML.     

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.     

Dopa and dopamine levels in the hypothalamus and brain stem of rats with experimental gastric ulcer treated by acupuncture

Department of Normal Physiology, Ivano-Frankovsk Medical Institute. Laboratory of Experimental and Clinical Biochemistry, Central Research Institute of Reflex Therapy, Ministry of Health of the USSR, Moscow. (Presented by Academician of the Accademy of Medical Sciences of the USSR K. V. Sudakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 3, pp. 274–279, March, 1989.     

Presumptive gamma-aminobutyric acid pathways from the midbrain to the superior colliculus studied by a combined horseradish peroxidase-gamma-aminobutyric acid transaminase pharmacohistochemical method

A pharmacohistochemical method for gamma-aminobutyric acid transaminase, the key enzyme for gamma-aminobutyric acid metabolism, has been combined with retrograde tracing by horseradish peroxidase, to a study of projections from the midbrain to the superior colliculus. The results indicate projections from the substantia nigra zona reticulata, the zona incerta and the reticular formation of the mesencephalon which are exclusively from neurons staining intensely for gamma-aminobutyric acid transaminase and presumptively gamma-aminobutyric acid as their transmitter. The projection from the ventral lateral geniculate body to the superior colliculus, on the other hand, comes from cells which do not stain for gamma-aminobutyric acid transaminase and therefore do probably not use gamma-aminobutyric acid as their transmitter.