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)     

The cerebellar projections to the superior colliculus and pretectum in the cat: An autoradiographic and horseradish peroxidase study

Efferent projections from the cerebellar nuclei to the superior colliculus and the pretectum have been studied using both retrograde and orthograde labeling techniques in the cat. In order to identify what parts of the cerebellar nuclei project to the superior colliculus and the pretectum, the retrograde horseradish labeling technique was employed. In another set of experiments, tritiated amino acids were injected into each of the cerebellar regions from which the cerebello-tectal and cerebellopretectal projections arise, and the laminar and spatial distributions of orthograde labeling in the superior colliculus and the pretectum were compared.The results showed that the cerebello-tectal projections arise from two different regions of the cerebellar nuclei: the caudal half of the medial nucleus and the ventrolateral part of the posterior interposed nucleus. Fibers arising from the medial nucleus distribute bilaterally in the superficial zone of the intermediate gray layer in the superior colliculus, while those originating from the posterior interposed nucleus terminate contralaterally in the deeper aspect of the intermediate gray layer and in the deep gray and white layers. Although the lateral nucleus does not contribute to the cerebello-tectal projection, it projects profusely to the pretectum contralaterally. The origin of the cerebello-pretectal projection lies in the parvicellular part of the lateral nucleus. Among several pretectal nuclei, the posterior pretectal, the medial pretectal nucleus and the reticular part of the anterior pretectal nucleus receive the cerebellar afferents.The findings of the differential projections from the cerebellum to the superior colliculus and the pretectum suggest that the cerebellum exerts a regulatory influence on visuo-motor and somato-motor transfer in these midbrain structures by differential circuits.     

Cortical projections to the periaqueductal grey in the cat: a retrograde horseradish peroxidase study

Stereotaxic fluid microinjections of horseradish peroxidase into different parts of the rostral and caudal periaqueductal grey (PAG) in cats have provided substantial retrograde evidence that the somatosensory cortex (I and II), frontal cortex, insular and cingular cortex are the principal sources of cortical-PAG projections. The somatosensory cortex II projects to all the regions of the rostral and caudal PAG. The frontal cortex projects to dorso-lateral quadrant of the PAG. The same projections were determined from insular and cingular cortex to PAG. The findings revealed a morphological substratum of corticofugal effects on PAG.     

Trigeminal primary afferent neurons projecting directly to the solitary nucleus in the cat: A transganglionic and retrograde horseradish peroxidase study

After applying horseradish peroxidase to peripheral branches of the trigeminal nerve in the cat, the lingual and pterygopalatine nerves were found to contain fibers which ended ipsilaterally in the rostral portions of the solitary nucleus (SN); massively in the medial and ventrolateral SN, moderately in the intermediate and interstitial SN and sparsely in the ventral SN. The rostralmost part of the SN was free from labeled terminals. After injecting the enzyme into the SN portions rostral to the area postrema, small neurons were scattered in the maxillary and mandibular divisions of the trigeminal ganglion.     

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     

Afferent connections of the zona incerta: a horseradish peroxidase study in the rat

Restricted microelectrophoretic injections either of free horseradish peroxidase or of horseradish peroxidase conjugated with wheat germ agglutinin were given to albino rats in order to study the afferent connections of structures of the subthalamic region. The results suggest that the zona incerta receives its main input from several territories of the cerebral cortex, the mesencephalic reticular formation, deep cerebellar nuclei, regions of the sensory trigeminal nuclear complex and the dorsal column nuclei. Substantial input to the zona incerta appears to come from the superior colliculus, the anterior pretectal nucleus and the periaqueductal gray substance, whereas many other structures, among which hypothalamic nuclei, the locus coeruleus, the raphe complex, the parabrachial area and medial districts of the pontomedullary reticular formation, seem to represent relatively modest but consistent additional input sources. The afferentation of neurons in Forel's fields H1 and H2 appears to conform to the general pattern outlined above. As pointed out in the Discussion, the present results provide hodological support for the classic concept according to which the zona incerta can be regarded as a rostral extent of the midbrain reticular core. Some of the possible physiological correlates of the fiber connections of the zona incerta in the context of the sleep-waking cycle, ingestive behaviors, somatic motor mechanisms, visual functions and nociceptive behavior are briefly discussed.     

Organization of diencephalic and brainstem afferent projections to the lateral septum in the rat

Ascending diencephalic and brainstem afferents to the lateral septal column were studied by retrograde transport of horseradish peroxidase following microiontophoretic injections in the various subdivisions of the lateral septal area. Predominantly ispilateral cells, of which several coincide with reported monoaminergic cell groups, appeared in the preoptic area, several hypothalamic nuclei, periventricular nuclei, raphe nuclei, pontine area and medulla oblongata. It is concluded that there is a heterogenous monoaminergic input to the lateral septal area organized in a complicated pattern along the longitudinal axis of the lateral septum.     

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

Summary Details of cerebellar afferent projections from the perihypoglossal nuclei were studied in the cat by means of retrograde axonal transport of horseradish peroxidase (HRP). Labeled cells were observed bilaterally (with a preponderance ipsilaterally) in nuclei intercalatus and praepositus hypoglossi following injections in various folia of the entire vermis, paraflocculus, flocculus, fastigial nucleus, and the nucleus interpositus anterior and posterior. Relatively high densities of labeled cells were found in nucleus intercalatus following injections in the anterior part of the vermis, whereas labeled cells in nucleus praepositus hypoglossi were found more frequently following injections in the posterior part of the vermis. Labeled cells in the nucleus of Roller were found only following injections in the anterior lobe vermis, posterior vermal lobules VI and VII, in the flocculus and in the nucleus interpositus anterior. No labeled cells could be detected in the three subdivisions of the perihypoglossal nuclei following HRP injections in crus I, crus II, paramedian lobule, and lateral cerebellar nucleus. The distribution of the HRP positive cells indicated the presence of a topographically organized projection from certain regions of the perihypoglossal nuclei to different parts of the cerebellum. The afferent and efferent connections of the perihypoglossal nuclei in relation to a functional role in eye and head movements are discussed.Abbreviations in Figures a,b,c sublobules of lobules V, VI and VII - f.apm. ansoparamedian fissure - f.icul. intraculminate fissure - f.in.cr. intercrural fissure - f.pc. preculminate fissure - f.pfl. parafloccular fissure - f.p.l. posterolateral fissure - f.ppd. prepyramidal fissure - f.pr. fissura prima - f.prc. precentral fissure - f.prc.a. precentral fissure a - f.p.s. posterior superior fissure - f.sec. fissura secunda - fl. flocculus - g.n. VII genu of facial nerve - HII-HVI, HIX hemispheral lobules II–VI, 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 - ic nucleus intercalatus - l.ans. ansiform lobule - N.f. nucleus fastigii - Nfc nucleus cuneatus - Nfg nucleus gracilis - N.i.a. nucleus interpositus anterior - N.i.p. nucleus interpositus posterior - N.l. nucleus lateralis - pfl.d. dorsal paraflocculus - pfl.v. ventral paraflocculus - Ph nucleus praepositus hypoglossi - Ro nucleus of Roller - S solitary tract - s.int.cr.1,2 intracrural sulcus 1 and 2 - SL lateral nucleus of the solitary tract - SM medial nucleus of the solitary tract - VIN inferior vestibular nucleus - VLD lateral vestibular nucleus, dorsal division - VMN medial vestibular nucleus - I-VI vermian lobules I–VI - VI nucleus of abducent nerve - VIIA,B; VIIIA,B anterior and posterior sublobules of lobules VII and VIII - IX uvula - X dorsal motor nucleus of vagus nerve; nodulus - XII nucleus of hypoglossal nerve Parts of this paper were presented at the Symposium Control of Gaze by Brain Stem Neurons, Paris, July 13–15, 1977On leave from the Laboratory of Neurobiology, Faculty of Science, Mahidol University, Bangkok, Thailand, under NORAD Fellowship Program from the Norwegian Agency for International Development     

Cortical neurons projecting to the pontine nuclei in the cat. An experimental study with the horseradish peroxidase technique

Summary Horseradish peroxidase (HRP) injections in various portions of the cat pontine nuclei resulted in retrograde labeling of neurons in layer V of the ipsilateral cerebral cortex.Corticopontine neurons, pyramidal in type, have been found to be labeled in the entire cortex, confirming the previous findings of anterograde degeneration studies. Most (91%) of the labeled cells were 14–26 m in diameter (mean 19.4±4.5 m SD). Small (10–20 m) and medium (20–40 m) cells represent 51.5% and 47.7%, respectively, of the total number of the labeled neurons. The populations of the neurons of various sizes were almost identical in different cortical areas, and were different from the populations of corticoreticular and corticospinal cells.Corticopontine cells were well labeled in experimental cases of 3-days' survival time, confirming the topographical organization established previously by degeneration studies for this projection system. However, in cases of shorter survival time (20–27 h), the number of labeled neurons was very small.The relative paucity of labeled Corticopontine neurons in the sigmoid and lateral gyri is discussed with reference to other cortical descending neurons (e.g., the corticotectal, corticoreticular and corticospinal) which have hitherto been identified morphologically as well as physiologically.Abbreviations AL gyrus lateralis anterior - ASigm gyrus sigmoideus anterior - ASup gyrus suprasylvius anterior - Br.p. brachium pontis - Cor gyrus coronalis - L left - L.m. lemniscus medialis - MEct gyrus ectosylvius medius - MSup gyrus suprasylvius medius - N.dl. nucleus dorsolateralis - N.l. nucleus lateralis - N.m. nucleus medianus - N.p. nucleus peduncularis - N.pm. nucleus paramedianus - N.r.t. nucleus reticularis tegmenti pontis - N.v. nucleus ventralis - Ped corticospinal and corticopontine fibers in cerebral peduncle - PSigm gyrus sigmoideus posterior - R right     

Afferent connections of the mesencephalic reticular formation: A horseradish peroxidase study in the rat

The afferent connections of the mesencephalic reticular formation were studied experimentally in the rat by the aid of the retrograde horseradish peroxidase tracer technique. The results suggest that the rostral portion of the mesencephalic reticular formation receives its main input from the cerebral cortex, the zona incerta and the fields of Forel, the central gray substance, the nuclei reticularis pontis oralis and caudalis, and the deep cerebellar nuclei. Substantial input to the same territory of the mesencephalic reticular formation appears to come from the superior colliculus, the substantia nigra, the parabrachial area, the spinal trigeminal nucleus, and the nucleus reticularis gigantocellularis, whereas several other brain structures, among which the locus coeruleus and the raphe complex, seem to represent modest but consistent additional input sources. The afferentation of more caudal portions of the mesencephalic reticular formation appears to conform to the general pattern outlined above with only three exceptions: the cerebral cortex, the deep cerebellar nuclei and the spinal trigeminal nucleus seem to be relatively modest sources of projections to these levels.Considering that the mesencephalic reticular formation is a critical structure in the “ascending activating systems”, the present results, confirming and extending those of many other investigators, characterize a set of pathways that seem to be an important part of the anatomical substrate of the sleep-waking cycle.     

Periaqueductal grey projection to the ventrobasal complex in the cat: An horseradish peroxidase study

Horseradish peroxidase (HRP) was injected within the thalamic ventrobasal complex of 14 cats. The aim was to ascertain whether the periaqueductal grey matter (PAG) sends fibres to this complex. Retrogradely labelled cells were found within the PAG following HRP delivery either in the nucleus ventralis posterolateralis (VPL) or ventralis posteromedialis (VPM). PAG-VPL projection is only ipsilateral and arises mainly from lateral PAG. PAG-VPM projection is bilateral and originates from latero-ventral regions of the central grey. The hypothesis that PAG might control the activity of ventrobasal nociceptive neurones is proposed.     

Retinal projection to the nucleus of the optic tract in the cat as revealed by retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase injected iontophoretically into the nucleus of the optic tract of cats revealed that the direction-selective cells in this pretectal nucleus receive direct retinal projections from small retinal ganglion cells, the so-called gamma-cells. These cells from a horizontal band on the contralateral retina. Few labeled cells are found in the ipsilateral temporal retina. The input from the contralateral retina is 10 times more numerous than from the ipsilateral one. In both retinae the highest concentration of labeled cells is near the area centralis.     

The primary afferent projection of the greater petrosal nerve to the solitary complex in the rat, revealed by transganglionic transport of horseradish peroxidase

The primary afferent projection of the greater petrosal nerve (GPN) to the solitary complex was studied following application of horseradish peroxidase (HRP) to the GPN just distal to the geniculate ganglion. Labeled fibers were traced to the most rostral part of the solitary tract. Numerous collaterals entered the solitary complex from its dorsal and lateral aspects, and formed a dense plexus. They terminated in the dorsal half of the medial solitary nucleus at the level of the rostral half of the solitary complex, and in the ventrolateral and commissural nuclei at the level of the caudal half. The densest termination was observed in the medial solitary nucleus. Labeled terminals were found to contain round, clear synaptic vesicles and to make asymmetrical synaptic contacts with dendritic profiles.     

The lateral reticular nucleus in the cat—I. An experimental anatomical study of its spinal and supraspinal afferent connections

The localization of the neurons from which the main ascending and descending projections to the lateral reticular nucleus originate has been studied in nine cats, using the retrograde axonal transport of horseradish peroxidase injected within that nucleus. The ascending spinoreticular neurons are widely distributed from the cervical to the sacral segments of the spinal cord. These neurons, which are of different sizes, are mainly located within Rexed's laminae VI, VII and VIII, but they spread both dorsally to laminae II–VI as well as ventrally to lamina IX. Labeled neurons of a size similar to motoneurons are particularly found within lamina IX, intermingled with the motoneurons. The spinal projection to the lateral reticular nucleus is crossed and uncrossed, with the ipsilateral spinoreticular neurons being located more dorsally within the grey matter of the spinal cord than the contralateral spinoreticular neurons. Moreover, while neurons with a crossed ascending projection are almost equally distributed along the whole rostro-caudal extension of the spinal cord, those with an uncrossed projection are predominantly located within the cervical segments of the spinal cord. Additional evidence indicates that the spinoreticular projection to the lateral reticular nucleus is somatotopically organized.In addition to the spinoreticular projection, the lateral reticular nucleus receives a crossed rubroreticular projection and a crossed fastigioreticular projection originating from the rostro-ventralmost part of the nucleus. A few neurons in the interposite nuclei also project to the lateral reticular nucleus.     

Cells of origin of brainstem afferents to lobules I and II of the cerebellar anterior lobe in the cat

Cells of origin of the brainstem afferents to lobules I and II of the cerebellar anterior lobe were identified by means of the retrograde horseradish peroxidase technique. In order to avoid diffusion into other lobules, injections were made under direct visual control through the fourth ventricle, after having removed ventral parts of the posterior lobe.With clearcut localization, the major projections originated from neurons of the following nuclei; the pontine nuclei (dorsal to the lateral nucleus, and the lateral and dorsal part of the peduncular nucleus) and nucleus corporis pontobulbaris; vestibular nuclear complex (the superior, medial and descending vestibular nuclei and group x), nucleus of Martin and interstitial nucleus of the vestibular nerve; the ventrolateral part of the external cuneate nucleus; lateral reticular nucleus (mainly the parvocellular portion); the inferior olivary complex (the caudal and central parts of the medial accessory nucleus and the lateral part of the dorsal accessory nucleus at middle levels). Small projections originated from the paramedian reticular nucleus, prepositus hypoglossi nucleus, nuclei raphe obscurus and pallidus, and the gracile and main cuneate nuclei.It was suggested that lobules I and II function not only as representations of the hindlimb-tail regions but also of the neck region by receiving afferents from the central cervical nucleus and the ventrolateral part of the external cuneate nucleus that receives dorsal root afferents C1 to C4.     

Corticocortical projections to the prefrontal cortex in the rhesus monkey investigated with horseradish peroxidase techniques

The corticocortical afferents innervating the prefrontal cortex in the monkey were studied by means of the retrograde axonal transport of horseradish peroxidase. After injection of small amounts (0.3-0.5 microliter) of this enzyme into various parts of the prefrontal cortex, many labeled neurons (mostly pyramids of 15-25 microns in diameter) were found in various cortical regions of the ipsilateral hemisphere. A small part of the prefrontal cortex received fibers from other parts of the same cortex. For example, area 8 receives many fibers from both the rostral part of area 9 and a small area adjacent to the inferior branch of the arcuate sulcus. On the other hand, area 9 in the inferior prefrontal convexity receives fibers from localized parts of areas 8 and 9 in the dorsolateral convexity as well as from area 6. It is also apparent that association connections from the dorsolateral to the inferior convexity are stronger than those going in the opposite direction. The prefrontal afferents from other cortical regions include many fibers originating from the posterior association cortex as well as some fibers arising in the cingulate and orbital gyri. The prefrontal cortex does not receive direct corticocortical fibers from the motor and "primary" sensory cortices. There is a topographic pattern in the prefrontal projections from the cortical walls (STs area) surrounding the superior temporal sulcus. Thus, the caudal half of the STs area projects to area 8 and a small adjacent part of area 9. The dorsal wall of the rostral half of the STs area projects to areas 9-12, the fundus to the inferior convexity, and the ventral wall only to the caudal part of the convexity. Projections from the circumjacent association cortex of the STs area to the prefrontal cortex as well as to the STs area are likewise found to be topographically organized. This suggests that certain parts of the posterior association cortex projecting to particular areas of the prefrontal cortex, also send fibers to those parts of the STs area which project to the same prefrontal areas.     

Identification of motoneurons supplying the tensor veli palatini muscle in the guinea pig and cat: An horseradish peroxidase study

Identification of motoneurons supplying the tensor veli palatini muscle was attempted by the horseradish peroxidase (HRP) method in the guinea pig and cat. After HRP injection into the tensor veli palatini muscle, HRP-labeled neurons were seen in the regions closely medial to the cluster of the lateral pterygoid motoneurons in the dorsolateral division of the trigeminal motor nucleus. In the guinea pig the tensor veli palatini motoneurons were observed at the level of the whole rostrocaudal extent of the trigeminal motor nucleus, while in the cat they were seen at the level of the rostral two-thirds of the 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     

Direct projections of the hypothalamic nuclei to the thalamic mediodorsal nucleus in the cat

Direct projections of the hypothalamic nuclei to the thalamic mediodorsal nucleus (MD) were studied using retrograde and anterograde transport of horseradish peroxidase (HRP) and wheat germ agglutinin (WGA)-HRP. HRP and WGA-HRP were injected into the MD, thalamic paraventricular, lateral habenular and hypothalamic nuclei. The results indicate that the MD, particularly its medial part, receives a moderate amount of hypothalamic afferents, and that most of these afferents originate in the medial part of the lateral hypothalamic nucleus at anterior levels, while a limited number are derived from the dorsal, dorsomedial, ventromedial and anterior hypothalamic and lateral preoptic nuclei.