Neurons at the origin of the medical component of the bulbopontine spinoreticular tract in the rat: An anatomical study using horseradish peroxidase retrograde transport

An anatomical technique based on the retrograde transport of horseradish perodidase (HRP) was used to investigate the progections of sponal cord neurions to the reticular formations in the rat. Both large and restricted injections were staggered all along the bulbar and pontine levels, involving the nucleus gigantocellularis, the nuclei reticularis pontis, pars oralis and cauladis and in some cases the nucleus raphé magnus. Labeled cells we constantly encountered in the reticular part of the neck of the dorsal horn throughout the whole length of the cord, mainly contralateral to the central core of the injection iste. This area was taken as the equivalent of lamina V in the cat. Other labeled cells were observed in the medial arts of the intermediate and ventral horns, in areas considered similar to laminae VII and VIII in the cat. The two most rostral cervical nating form the dorsolateral part of ventral horns. Thus, this study is a clear confirmation that the bulbopontine reticular formations constitute a target for various somatosensory inputs originating in spinal cord. It demonstrates that the medial spinoreticular tract (mSRT) differs from the other main ascending tracts by the absence of projections from (1) superficial layers and nucleus of the dorsolateral funiculus contrary to the spinomesencephalic tract; (2)ventromedial zone of the lumber dorsal horn unlike the spinothalamic tact; (3) the neck of the doral hor in its medial portuion contrary to the spinoreticular component reaching the lateral reticular nucleus; and (4) central cervical nucleus and Clarke's columns, unlike the spinocerebellar tracts. The difficulty in demonstrating retrograde labeling from discrete injections coulde result from the fact that mSRT neu-rons have sparsely ramified collaterals on their terminal zones.     

Segmental distribution and central projectionsof renal afferent fibers in the cat studied by transganglionic transport of horseradish peroxidase

The segmental and central distributions of renal nerve afferents in adult cats and kittens were studied by using retrograde and transganglionic transport of horseradish peroxidase (HRP). Transport of HRP from the central cut ends of the left renal nerves labeled afferent axons in the ipsilateral minor splanchnic nerves and sensory perikarya in the dorsal root ganglia from T12 to L4. The majority of labeled cells (85%) were located between L1 and L3. A few neurons in the contralateral dorsal root ganglia were also labeled. Labeled cells were not confined to any particular region within a dorsal root ganglion. Some examples of bifurcation of the peripheral and central processes within the ganglion were noted. A small number of preganglionic neurons, concentrated in the intermediolateral nucleus, were also identified in some experiments. In addition, many sympathetic postganglionic neurons were labeled in the renal nerve ganglia, the superior mesenteric ganglion, and the ipsilateral paravertebral ganglia from T12 to L3 Transganglionic transport of HRP labeled renal afferent projections to the spinal cord of kittens from T1 1 to L6, with the greatest concentrations between Ll and L3. These afferents extended rostrocaudally in Lissauer's tract and sent collaterals into lamina I. In the transverse plane, a major lateral projection and a minor medial projection were observed along the outer and inner margins of the dorsal horn, respectively. From the lateral projection many fibers extended medially in laminae V and VI forming dorsal and ventral bundles around Clarke's nucleus. The dorsal bundle was joined by collaterals from the medial afferent projection and crossed to the contralateral side. The ventral bundle extended into lamina VII along the lateroventral border of Clarke's nucleus. Some afferents in the lateral projection could be followed ventrally into the dorsolateral portion of lamina VII in the vicinity of the intermediolateral nucleus. In the contralateral spinal cord, labeled afferent fibers were mainly seen in laminae V and VI These results provide the first anatomical evidence for sites of central termination of renal afferent axons. Renal inputs to regions (laminae I, V, and VI) containing spinoreticular and spinothajamic tract neurons may be important in the mediation of supraspinal cardiovascular reflexes as well as in the transmission of activity from nociceptors in the kidney. In addition, the identification of a bilateral renal afferent projection in close proximity to the thoracolumbar autonomic nuclei is consistent with the demonstration in physiological experiments of a spinal pathway for the renorenal sympathetic reflexes.     

Anatomical studies on the nucleus reticularis tegmenti pontis in the pigmented rat. II. Subcortical afferents demonstrated by the retrograde transport of horseradish peroxidase

The subcortical nuclear groups projecting to the nucleus reticularis tegmenti pontis (NRTP) were studied in pigmented rats with the aid of the retrograde horseradish peroxidase (HRP) technique. Small iontophoretic injections of HRP were placed in the medial regions of the NRTP, an area that has been shown in several species to be involved in eye movements. Other large injections in the NRTP or small injections placed just outside the nucleus were used to clarify the projections to the NRTP. Results indicate that the NRTP receives afferents from visual relay nuclei, including the nucleus of optic tract, the superior colliculus, and the ventral lateral geniculate nucleus; oculomotor-associated structures including the zona incerta, the H1 and H2 fields of Forel, the nucleus subparafasciculus, the interstitial nucleus of Cajal, the visual tegmental relay zone of the ventral tegmental area of Tsai, the mesencephalic, pontine, and medullary reticular formations, the nucleus of the posterior commissure, and a portion of the periaqueductal gray termed the supra-oculomotor periaqueductal gray; cerebellar and pontomedullary nuclei, including the superior, lateral, and medial vestibular nuclei, the deep cerebellar nuclei, and NRTP interneurons, and nuclei related to limbic functions including the lateral habenula, the mammillary nuclei, the hypothalamic nuclei, the preoptic nuclei, and the nucleus of diagonal band of Broca. A surprisingly large number of afferents to the medial regions of the NRTP arise from visual- or eye-movement-related nuclei. The projection from the nucleus of the optic tract (NOT) confirms previous anatomical and physiological studies on the pathways involved in horizontal optokinetic nystagmus, but the number of NOT afferents is small in relation to other areas potentially related to visuomotor pathways such as the zona incerta, ventral lateral geniculate nucleus, fields of Forel, perirubral area, and subparafasciculus. The NRTP may also relay information related to vertical visuomotor reflexes (e.g., vertical optokinetic nystagmus) given the strong projections from the medial terminal nucleus of the accessory optic system, visual tegmental relay zone, supra-oculomotor periaqueductal gray, interstitial n. of Cajal, and midbrain reticular formation. The presence of significant NRTP projections from the superior colliculus and the mesencephalic and pontine reticular formations suggests that these nuclei may provide the pathways for the noted saccade-related activity of NRTP neurons. In addition, projections from the vestibular nuclei were found that provide the anatomical basis for head velocity signals recorded in NRTP neurons.(ABSTRACT TRUNCATED AT 400 WORDS)     

The efferent projections from the reticular formation and the locus coeruleus studied by anterograde and retrograde axonal transport in the rat

Following injections of [3H]leucine into the formatio reticularis gigantocellularis (Rgc), reticularis pontis caudalis (Rpc), reticularis pontis oralis (Rpo), reticularis mesencephali (Rmes), or the locus coeruleus (LC) of the rat, autoradiographic study revealed prominent reticuloreticular projections from all areas and secondary projections onto cranial nerve motor nuclei from most areas within the brain stem. Common long descending projections extended the full length of the spinal cord terminating in the ventromedial ventral horn and intermediate zone and more sparsely in the base of the dorsal horn and (particularly from Rgc) the region of the motoneurons. Common long ascending projections extended into the forebrain via Forel's tegmental fascicles. A dorsal branch of fibers innervated the intralaminar and midline nuclei of the thalamus. The major fiber system continued forward through Forel's fields and ascended into the pallidum from Rpo, Rmes, and LC and into the neostriatum from Rmes and LC. Fascicles from all areas also ascended in the medial forebrain bundle through the lateral hypothalamus to the lateral preoptic area, substantia innominata, and nuclei of the diagonal band. From Rpo, Rmes, and LC, fibers continued forward to reach the cerebral cortex, where the innervation was sparse and discrete from Rpo and Rmes but moderate and ubiquitous from LC. Retrograde transport of true blue and/or nuclear yellow revealed inverse gradients along the brain stem longitudinal axis of interdigitated cells respectively projecting caudally into the spinal cord (with the greatest number of cells in Rgc, Rpc, and Rpo) and rostrally into the diencephalon (with the greatest number of cells in Rmes and LC), with very few cells projecting both to the spinal cord and the diencephalon. From the basal forebrain, a large number of reticular and LC cells were retrogradely labelled, whereas from the frontal cortex, a much smaller number of reticular cells was labelled. These results document the widespread efferent projections from the reticular formation and overlapping, yet more extensive, projections from the LC.     

Spinal afferents to lamina IX of the cervical enlargement in the rat studied by the retrograde transport of horseradish peroxidase

Spinal neurons that project to the ventrolateral, dorsolateral and ventromedial portions of lamina IX of the cervical enlargement in the rat were investigated by means of horseradish peroxidase retrograde transport. In the cervical and upper thoracic segments, labeled neurons were observed ipsilaterally in laminae V–VIII and contralaterally in laminae VII–VIII. In the lower thoracic and upper lumbar segments, labeled neurons were seen after HRP injection into the ventrolateral part of lamina IX, and were distributed mainly in the lateral parts of the ipsilateral laminae V–VI.     

Ascending projections to the mammillary nuclei in the rat: a study using retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase

Cells of origin of ascending afferents to the mammillary nuclei and the afferents' fields of termination within these nuclei were studied by using retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase in the rat. The pars compacta of the superior central nucleus projects bilaterally to the median region of the medial mammillary nucleus. The ventral tegmental nucleus projects ipsilaterally to the medial mammillary nucleus, except for its median region, in a topographic manner such that the rostrodorsolateral part of the ventral tegmental nucleus projects to the medial quadrant of the medial mammillary nucleus; the rostroventromedial part projects to the dorsal quadrant; the caudodorsolateral part projects to the ventral quadrant; and the caudoventromedial part projects to the lateral quadrant. These projection fields extend throughout the longitudinal axis of the medial mammillary nucleus, except for its most caudal region, to which only the dorsolateral part of the ventral tegmental nucleus projects. This nucleus also projects topographically to the ipsilateral dorsal premammillary nucleus; the rostral part of the ventral tegmental nucleus projects to the dorsal part of the dorsal premammillary nucleus, whereas the caudal part projects to the ventral part. The periaqueductal gray around the dorsal tegmental nucleus projects bilaterally to the supramammillary nucleus. The pars alpha of the pontine periaqueductal gray projects bilaterally to the peripheral part of the lateral mammillary nucleus, whereas the pars ventralis of the dorsal tegmental nucleus projects ipsilaterally to the lateral mammillary nucleus. The results show that the tegmentomammillary projections are organized in a gradient fashion, with the rostral to caudal position of cells of origin within the tegmental nuclei of Gudden being reflected by the medial to lateral position of fields of termination within the mammillary nuclei.     

Spinocerebellar projections from the central cervical nucleus in the cat, as studied by anterograde transport of wheat germ agglutinin-horseradish peroxidase

The projection of the spinocerebellar tract arising from the central cervical nucleus with crossed ascending axons was studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) in the cat. Following injections of WGA-HRP into the C1 to the C4 or C5 segments, labeled terminals were seen in lobules I-VI, sublobule VIIb, lobules VIII and IX, the paramedian lobule, crus I and crus II, and the simple lobule. About 67-80% of the total number of labeled terminals were in the anterior lobe and 20-33% in the posterior lobe; the labeled terminals were abundant in lobules I (11-20%), II (11-28%), III (5.7-9.6%), IV (8.6-15.4%), and VIII (9-12%). The labeled terminals were densely distributed in the basal half or basal two-thirds of sublobules IIa-Va and VIf-VIb in their apicobasal extent and the transitional areas between neighboring sublobules. In sublobules Ia, Ib, and Vg they were distributed over the entire sublobule. The labeled terminals were most abundant within 0.5 mm of the midline (30-55% of the total number in each sublobule). Results in cases with injections into the C2-C4 segments, preceded by hemisection between the C1 and C2 segments, revealed that the projections were bilateral but predominantly contralateral to the cells of origin; the proportion of the quantity of the contralateral projection to that of the ipsilateral was about 60:40% in sublobules Ia-Vb and sublobules Ve-Vg. The projection field in the horizontal plane of the lobule was reconstructed from a series of cross sections through each sublobule. The labeled terminals were distributed in three major longitudinal areas named areas 1, 2, and 3, respectively. These areas were confined in the basal half to two-thirds of lobules III-V: area 1 located in zone A1 of Voogd (within 0.25 mm of the midline); area 2 located in zones A1 to A2 (at around 0.5 mm lateral to the midline); and area 3 located in the lateral part of zone A2 to zone B (between 0.75 mm and 1.5 mm lateral to the midline in lobule III, and between 1.0 mm and 2.0 mm lateral to the midline in lobules IV-VI). An indefinite area 4 appeared in zones B and C of some lobules. In sublobules Ia, Ib, Vf, and Vg the three areas extended throughout the apicobasal length.(ABSTRACT TRUNCATED AT 400 WORDS)     

The organization of thalamocortical relay neurons in the rat ventrobasal complex studied by the retrograde transport of horseradish peroxidase.

The organization of thalamocortical relay neurons in the thalamic ventrobasal complex (VB) of the rat was investigated by the use of the retrograde axonal transport of horseradish peroxidase (HRP). Injections of HRP into somatosensory cortex (SI) resulted in a distinctive gradient of neuronal and non-neuronal HRP reaction product. Electrophysiologically characterized points of SI injected with small volumes of HRP labeled a sector of neurons in VB ipsilateral to the injection. This zone of labeled neurons consisted of a complex curvilinear array or lamina with a rostral hollow or solid expansion of densely packed HRP positive neurons which continues caudally as a less dense tapering wing. Despite this complex arrangement, an approximate pattern of somatotopy was determined indicating the direction of shifts in peripheral receptive fields moving in any axis of VB. The number of labeled neurons projecting upon a point in SI was also determined. Injections of the cortical vibrissae, face and forepaw representations labeled a greater number of neurons in VB per unit area of cortex than did injections in the hindlimb or body representations. The total number of HRP positive neurons in VB increased proportionately with areal increase of the HRP injections into overlapping cortical representations. The number of HRP positive neurons in the rostral half of the laminae increased almost linearly with the area of injection, while the number of HRP positive neurons in the caudal half of the laminae showed relatively smaller increases.     

Thalamostriatal neurons with collateral projection onto the rostral reticular thalamic nucleus: anatomical study in the rat by retrograde axonal transport of iron-dextran and horseradish peroxidase

Injection of horseradish peroxidase (HRP) into the head of the reticular thalamic nucleus (RT) of rats having undergone large cortical and striatal lesions, led to the labeling of thalamic neurons in medial thalamic nuclei. After injection of iron-dextran into the corpus striatum and HRP into the rostral RT of intact rats, double-labeled neurons were observed in the medial thalamus, mainly in the central lateral nucleus.     

Projections of medial terminal accessory optic nucleus, ventral tegmental nuclei, and substantia nigra of rabbit and rat as studied by retrograde axonal transport of horseradish peroxidase

Projections of the medial terminal nucleus (MTN) of the accessory optic system, the ventral tegmental area of Tsai, and the substantia nigra of the rabbit and the rat have been studied by the method of retrograde axonal transport of horseradish peroxidase. The data show that MTN projections are remarkably similar in the rabbit and rat. The MTN projects heavily to the ipsilateral nucleus of the optic tract and dorsal terminal nucleus of the accessory optic system and to a portion of the contralateral ventral tegmental area of Tsai that we have termed the visual tegmental relay zone (VTRZ). Further, the MTN sends projections to the ipsilateral mesencephalic (deep mesencephalic nucleus, pars medialis) and pontine (nucleus reticularis pontis oralis) reticular formations; the contralateral dorsolateral division of the basal pontine complex; the superior and lateral vestibular nuclei (contralateral in rat; bilateral in rabbit); and the ipsi- and contralateral interstitial nucleus of Cajal, nucleus of Darkschewitsch, and supraoculomotor-periaqueductal gray. The findings also indicate that the MTN has a small bilateral, but mainly ipsilateral, projection to the dorsal cap, its ventrolateral outgrowth, and the B division of the inferior olivary complex. This study further reveals that ventral tegmental nuclei (n. parabrachialis pigmentosus and n. paranigralis) and subdivisions of the substantia nigra (pars compacta and pars reticulata) project to many brain stem targets of the MTN. Thus, the VTRZ projections are similar to those of the MTN in both distribution and density except that the VTRZ projection to the inferior olive is substantially stronger. The nucleus parabrachialis pigmentosus sends a small contralateral projection to the VTRZ and a moderate-sized bilateral projection to the supraoculomotor-periaqueductal gray. The nucleus paranigralis sends a moderate number of axons to the ipsilateral deep mesencephalic nucleus, pars medialis, and the nucleus reticularis pontis oralis and provides a strong bilateral projection to the supraoculomotor-periaqueductal gray. The pars compacta of the substantia nigra provides a sparse input to the ipsilateral deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and to the contralateral VTRZ and sends a moderate number of axons, bilaterally, to the supraoculomotor-periaqueductal gray.The pars reticulata of the substantia nigra sends an ipsiateral projection of moderate size to the intermediate and deep layers of the superior colliculus, sparse ipsilateral projections to the deep mesencephalic nucleus, pars medialis, and nucleus reticularis pontis oralis, and a sparse bilateral projection to     

Spinal projections from the nucleus locus coeruleus and nucleus subcoeruleus in the cat and monkey as demonstrated by the retrograde transport of horseradish peroxidase

The rostral pons of the cat and rhesus monkey were examined for the presence of labeled cells following injections of horseradish peroxidase (HRP) into the lumbar spinal cord. Labeled cells were found in the ipsilateral dorsolateral pontine tegmentum and in the contralateral ventrolateral pontine reticular formation. In both the cat and monkey, labeled cells were located in the nucleus locus coeruleus, nucleus subcoeruleus, in or near the Kölliker-Fuse nucleus, and in the ventral part of the lateral parabrachial nucleus. There is a striking similarity between the distribution of HRP-labeled cells in the dorsolateral pontine tegmentum of the cat and monkey and that of catecholamine-containing cells observed in this area in previous studies.     

Bonyfish lateral line efferent neurons identified by retrograde axonal transport of horseradish peroxidase (HRP)

Post-mortem brain tissue from 7 patients who died with a diagnosis of senile dementia of Alzheimer type (SDAT) was compared with tissue obtained from 7 control patients at routine post mortem. A significant fall in choline acetyltransferase (ChAT) activity was apparent in the cerebral cortex of the SDAT cases which was maximal in the temporal lobe. The fall in ChAT activity was not accompanied by changes in cortical vasoactive intestinal polypeptide (VIP) measured by radioimmunoassay.     

Afferent projections to the interpeduncular nucleus in the rat, as studied by retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase

We examined the afferent projections to the subnuclei of the interpeduncular nucleus (IPN) in the rat by means of retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). We observed locations of retrogradely labeled cells following injections of WGA-HRP into the IPN, and distributions of anterogradely labeled fibers and terminals within the IPN following injections into the areas that contain cells of origin of afferents. Results of the retrograde and anterograde experiments have clarified the detailed organization of the IPN afferents. A part of the nucleus incertus, located dorsomedial to the dorsal tegmental nucleus, projects to the contralateral half of the rostral subnucleus of the IPN; the pars caudalis of the dorsal tegmental nucleus projects sparsely to the rostral lateral, dorsal lateral, lateral, caudal, and apical subnuclei predominantly contralaterally; the laterodorsal tegmental nucleus, to most of the subnuclei predominantly contralaterally; the ventromedial central gray rostral to the dorsal tegmental nucleus and lateral to the dorsal raphe nucleus projects to the rostral lateral and dorsal lateral subnuclei predominantly contralaterally; the median raphe nucleus, substantially to all subnuclei; the medial habenular nucleus, in a topographic manner, to the rostral, central, and intermediate subnuclei, to the rostral lateral and lateral subnuclei predominantly ipsilaterally, and to the dorsal lateral subnucleus predominantly contralaterally; the supramammillary nucleus and areas around the origin of the mammillothalamic tract and near the third ventricle project sparsely to the ventral part of the rostral subnucleus and to the central, lateral, caudal and apical subnuclei; the nucleus of the diagonal band, sparsely to the rostral, central, dorsal lateral, caudal, and apical subnuclei. These differential projections of the afferents to the subnuclei of the IPN may reflect its complex functions within the limbic midbrain circuit.     

Some claustro-cortical connections in the cat and baboon as studied by retrograde horseradish peroxidase transport.

1. The mammalian Claustrum (Cl) is a convergent multisensory structure of unknown function, and disputed ontogenetic origin. Its cortical projections, hitherto unknown, have been studied in cat and baboon by means of the horseradish peroxidase (HRP) technique. HRP was injected into the gyrus proreus (frontal eye field) of cats, and separately into the frontal eye fields, visual areas, and motor-premotor areas of the baboon cortex. 2. Differential retrograde transport to the Cl was demonstrated, such that in the cat the ipsilateral dorsal Cl was shown to be the principal origin of claustroproreate projections. In the baboon, the whole Cl projects onto area 8, while only the posteroventral part of the nucleus sends efferents to the visual cortex. The projection to the motor and premotor areas is present, but does not seem to be "essential." 3. Discussion of the physiological literature, together with anatomical evidence of reciprocal cortico-claustral projections to closely similar regions of the Cl lead to the suggestion that the Cl is concerned with the integration of messages subserving visually-directed movements. Some other functional implications are also discussed.     

The central projections of tooth pulp afferent neurons in the rat as determined by the transganglionic transport of horseradish peroxidase

Transganglionic transport of horseradish peroxidase (HRP) or horseradish peroxidase-wheat germ agglutinin conjugate (HRP-WGA) was used to map in detail the central projections of trigeminal primary afferent neurons that innervate the dental pulp organ of the rat. In each of ten animals, 0.5-2.0 microliters of enzyme solution was injected into the pulp chamber of the first maxillary molar tooth. Postmortem examination of the decalcified teeth in all cases showed that the HRP/HRP-WGA remained confined to the pulp chamber and pulp roots, with no spread of enzyme into periapical tissues. HRP-labeled tooth pulp afferent fibers projected to all four rostrocaudal subdivisions of the ipsilateral trigeminal brainstem nuclear complex (TBNC) and to the upper cervical spinal cord. The labeled terminal fields formed a column that stretched relatively uninterrupted from just caudal to the rostromedial tip of the trigeminal principal sensory nucleus to at least the C2 segment of the spinal cord. The density of the afferent projection varied markedly from one rostrocaudal level of the TBNC to the next but was heaviest in an area encompassing the caudal one-half of the principal sensory nucleus and the rostral two-thirds of pars oralis. Fibers projected only lightly to pars caudalis, where they terminated preferentially in laminae I, IIa, and the junctional zone between laminae IV and V. HRP-labeled terminals in C1 and C2 were located almost exclusively in laminae I. In the dorsoventral axis, the terminal fields in the TBNC were located in a surprisingly dorsal part of the complex, well within what has been shown by others to be largely an area of termination for mandibular division fibers. Most fibers ended in medial parts of the TBNC, with the exception of two modestly labeled terminal fields located in the lateral aspects of rostral pars oralis and rostral pars caudalis. No labeled fibers terminated in the contralateral TBNC or contralateral cervical spinal cord.     

Olivocerebellar connections in sheep studied with the retrograde transport of horseradish peroxidase

We describe here the morphology of the inferior olive and the localization of labeled cells after HRP injections into various lobules of vermis and hemisphere of the cerebellum of the sheep. The medial part of the caudal half of the medial accessory olive projects to a medial zone in the anterior lobe, the simple lobule, and the lobules VII and VIII. The lateral part of the medial accessory olive projects to more lateral parts of these lobules with the exception of lobule VII. The group beta projects in a differential manner to the lateral parts of the lobules VII and VIII and the medial parts of the lobules IX and X. The dorsomedial cell column projects to lobules VIII, IX, and X; the connections of the dorsal cap are restricted to lobule X. Fibers from the caudal limb of the dorsal accessory olive terminate in the B zone, the simple lobule, and in lobule VIII. The rostral half of the medial accessory olive projects to lobule IX and to the hemisphere. The other projections of the accessory olives and the principal olive to the hemisphere are similar to those reported for the cat. An accessory cell group in the sheep, located between the principal and the dorsal accessory olive, has connections with the caudal vermis and the hemisphere.     

Efferent connections of the caudate nucleus of the cat studied using retrograde axonal transport of horseradish peroxidase

The origin of descending efferent pathways from the caudate nucleus was studied by retrograde axonal transport of horseradish peroxidase. Widespread topically organized projections were observed to the paleostriatum and the substantia nigra and less numerous to the thalamus. The main source of these projections were small and medium-size cells. A particular role of the subthalamic nucleus in the descending efferent system of the caudate nucleus is pointed out: this nucleus besides projections to the caudate nucleus itself possesses direct connections with principal output structures of the latter--the the paleostriatum and substantia nigra.     

The inferior olivary connections to the cerebellum in the rat studied by retrograde axonal transport of horseradish peroxidase

Olivocerebellar projections were investigated in the rat using retrograde axonal transport of horseradish peroxidase. Discrete cell groups of the inferior olive were labelled, subsequent to injections in the paravermal region, the vermis, or the caudolateral hemisphere. Injections in the midrostrocaudal third of the paravermal area resulted in labelling of cells in the medial accessory olive (MAO), in cell group “b” at caudal levels, and in its lateral portion at mid-rostrocaudal levels. The rostral pole of the principal olive (PO), the dorsal accessory olive (DAO), and the dorsomedial cell column, were heavily labelled. By comparison, caudal paravermal injections resulted in labelling in the medial part of the mid-rostrocaudal levels of the MAO, but not in its caudal portion. The PO lamellae were labelled in their lateral half, excluding the lateral bend connecting them. Injections slightly lateral within this paravermal area gave no caudal MAO labelling, but did label cells in segments of both PO lamellae, medial to those in the previous case. From vermal injections, cell groups “b” and “c” of the caudal MAO were labelled, but no labelled cells were present in the PO. Subsequent to injections in the paramedian lobule, cells in the dorsal lamella of the PO were labelled. No cells of the MAO were labelled. These results are discussed in terms of specific labelling patterns and the general concepts of organization presently held for the Olivocerebellar system.