Thalamic projections to motor, prefrontal, and somatosensory cortex in the sheep studied by means of the horseradish peroxidase retrograde transport method.

In this study the motor, prefrontal, and somatosensory areas of the sheep cerebral cortex were defined on the basis of their thalamic afferents traced with the horseradish peroxidase method. The motor area (areas 4 and 6) occupies the cruciate gyrus. It receives a substantial projection from the thalamic nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and centralis lateralis and a smaller one from the nuclei ventralis medialis, centralis medialis, paracentralis, lateralis dorsalis, lateralis posterior, centromedianus, parafascicularis, suprageniculatus, ventralis posterolateralis, and the midline nuclei. Area 4 receives afferents mainly from the nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and lateralis posterior, whereas area 6 receives afferents mainly from the nuclei ventralis anterior, medialis dorsalis, and lateralis posterior and fewer afferents from the nucleus ventralis medialis. The prefrontal area occupies the gyrus proreus and receives numerous afferents from the nucleus medialis dorsalis and fewer from the nuclei lateralis posterior and ventralis medialis. The area extending between the lateral fissure, the coronal sulcus, the presylvian sulcus, and the rostral branch of the lateral fissure is connected mainly with sensory thalamic nuclei. Thalamic afferents were found to emanate from the nuclei ventralis posteromedialis (its parvicellular part included), ventralis posterolateralis, ventralis medialis, paracentralis, lateralis posterior, medialis dorsalis, centromedianus, suprageniculatus, paraventricularis, the substantia nigra, and the ventral part of the lateral geniculate nucleus. The first somatosensory area (Johnson et al., '74, J. Comp. Neurol. 158:81-108) was found to extend between the coronal, the diagonal, and the anterior suprasylvian sulci and to receive afferents almost exclusively from the nucleus ventralis posteromedialis.

Somatostatinlike immunoreactive neurons in the hedgehog (Erinaceus europaeus) and the sheep (Ovis aries) central nervous system.

The morphology and distribution of somatostatinlike immunoreactive perikarya in the central nervous system of the hedgehog and sheep have been studied by means of the peroxidase-antiperoxidase immunohistochemical method. Intracerebroventricular colchicine infusion not only enhanced the immunostaining but also revealed new immunoreactive cell bodies. In both hedgehog and sheep immunoreactive neurons of various forms, ranging from 12 to 28 microns in diameter, were observed in a number of homologous brain structures. However, some species-related differences were noticed. Thus, somatostatinlike immunoreactive neurons were found only in the hedgehog anterior olfactory nucleus, olfactory tubercle, nucleus accumbens, medial parabrachial nucleus, raphe nuclei of the medulla, and spinal trigeminal nucleus, whereas some somatostatin-positive neurons were observed in the locus coeruleus and the pontine reticular formation of the sheep only. Mapping of peptides in species like sheep and hedgehog, with basically different orientations of living behaviour, may contribute in strengthening or extending our views concerning the role of peptides in the central nervous system of mammals.

Neurotensinlike immunoreactive neurons in the hedgehog (Erinaceus europaeus) and the sheep (Ovis aries) central nervous system.

Neurotensin-containing neurons in the hedgehog and sheep central nervous system were studied immunohistochemically. In both species, mapping of neurotensin neurons was achieved only after pretreatment with colchicine injected intracerebroventricularly 2 days prior to perfusion. Bipolar or multipolar neurotensin neurons, 10-30 micron in diameter, were observed in the following regions of the central nervous system of both species: medial amygdaloid nucleus, lateral septal nucleus, interstitial nucleus of the stria terminals, caudate nucleus, preoptic area, and hypothalamus. On the contrary, while immunoreactive neurons were found in the central amygdaloid nucleus, nucleus accumbens, nucleus of the diagonal band, subthalamus, superior central nucleus, dorsal raphe nucleus, central gray substance of the pons, and dorsal horn of the spinal cord of the hedgehog, respective regions of the sheep appeared to be devoid of immunoreactive perikarya. Also, in some regions, namely the hippocampal formation, the central gray substance of the midbrain, the locus coeruleus, and the nucleus of the solitary tract, neurotensin neurons were found exclusively in the latter species. The existence of these differences in the distribution pattern of neurotensin-immunoreactive neurons between the two species as well as between them and others already examined is briefly discussed.

VIP- and CCK-like-immunoreactive neurons in the hedgehog (Erinaceus europaeus) and sheep (Ovis aries) brain.

The distribution pattern and the morphology of vasoactive intestinal polypeptide (VIP)- and cholecystokinin (CCK)-like-immunoreactive neurons were studied in the brain of the hedgehog and the sheep by means of the peroxidase-antiperoxidase immunocytochemical method. A total of 34 hedgehogs and 26 sheep of both sexes were used. Fourteen hedgehogs and 13 sheep received an intracerebroventricular injection of colchicine that enhanced the immunostaining and revealed "new" immunoreactive cell bodies. VIP-immunoreactive bipolar and multipolar neurons were observed in both species in the cerebral cortex, hippocampal formation, amygdaloid complex, hypothalamus, and central gray substance of the midbrain. CCK-immunoreactive bipolar, bitufted, and multipolar neurons displayed a broader distribution in both mammals than VIP neurons and were found in the cerebral cortex, the hippocampal formation, the amygdaloid complex, the hypothalamus, the mesencephalon, and the pons. In the cortex, in both the hedgehog and the sheep, VIP neurons were located in all layers but were concentrated in layers II and III, with the majority being typical bipolar. CCK neurons were more numerous in the superficial layers (I-III) but were found in the deep layers as well. They were bipolar, bitufted, or multipolar in morphology. From these neurons a small percentage, which were located almost exclusively in layers II and III of the visual cortex, exhibited also VIP immunoreactivity. Perikarya of such double-labeled cells were ovoid or round in shape with one or two main processes emanating from each pole of the cell body and oriented perpendicularly to the pia. The coexistence of the two peptides within individual neurons of the cortex has not been reported in other species and its physiological significance is discussed in relation to the GABAergic neurons of the cortex.

Visual thalamocortical connections in sheep studied by means of the retrograde transport of horseradish-peroxidase.

In order to study the visual thalamocortical connections in the sheep, horseradish peroxidase (0.3--0.5 microliter of a 30% solution) has been injected in the gyri marginalis, ectomarginalis medius pars medialis, ectomarginalis medius pars lateralis and ectosylvius caudalis. The results show that: (1) the dorsal lateral geniculate nucleus (LGNd) projects to the former three gyri. Dorsal parts of the LGNd project to caudal areas, whereas its ventral parts project to rostral areas of these gyri; medial parts of the LGNd project to the gyrus ectomarginalis medius pars lateralis, while lateral parts project to the gyrus marginalis; (2) the medial interlaminar nucleus (MIN) or pars geniculata pulvinaris of Rose ('42b) projects to the caudal part of the gyrus marginalis and to the gyrus ectomarginalis medius pars lateralis; (3) the pulvinar proper of Rose (PUL) projects to the caudal part of the gyrus ectosylvius caudalis whereas the rostral part of this gyrus receives input from the medial geniculate body. In relation to Rose's cytoarchitectonic study of the cortex of sheep ('42a) the present study has shown that the LGNd projects to both the area striata (gyrus marginalis + gyrus ectomarginalis medius pars medialis) and area occipitalis (gyrus ectomarginalis medius pars lateralis) of Rose, that the gyrus marginalis and the area occipitals receive a second projection (from the MIN), and that the PUL projects beyond the area occipitalis to the area parietalis of Rose.

Claustrum in the hedgehog (Erinaceus europaeus) brain: cytoarchitecture and connections with cortical and subcortical structures.

The cytoarchitecture of the claustrum in the hedgehog (Erinaceus europaeus) brain, the morphology of its neurons, and the efferent connections with cortical and subcortical structures were studied with the Nissl and Klüver-Barrera, the Golgi, and the horseradish peroxidase methods. It was found that the claustrum is a well developed nucleus in the hedgehog telencephalon and, as in other mammals, is divided into dorsal and ventral parts. In Golgi-stained sections, spiny multipolar cells are the predominant neurons of both the dorsal and the ventral claustrum and are projection neurons. Aspiny multipolar neurons with fewer, often beaded, dendrites constitute a minority in both divisions and are interneurons. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the prefrontal, motor, somatosensory, auditory and visual areas, and HRP or WGA-HRP injections in the thalamus showed that: (1) the claustroneocortical projections originate in the dorsal claustrum and are distributed to the entire neocortex; these projections are mainly ipsilateral but some also originate contralaterally; (2) the claustroneocortical projections show a rough topographic organization; there exists a substantial degree of overlap; and (3) the claustrothalamic projection, arising throughout the dorsal claustrum, is strictly ipsilateral. No evidence of a thalamoclaustral projection was found. The present results suggest that, although the hedgehog has been referred to as a "paleocortical mammal" owing to the great development of its rhinencephalic structures in comparison with its small neocortex, the dorsal claustrum is well developed and is connected with all neocortical areas as well as with the thalamus, establishing it as a key structure in the hedgehog forebrain.

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.

Secondary trigeminocerebellar projections in sheep studied with the horseradish peroxidase tracing method.

Secondary trigeminocerebellar connections have been studied with HRP histochemistry in 25 sheep. The results indicate that almost all of the cerebellar cortex except flocculus, ventral paraflocculus and lobules I-IV receives bilateral (mostly ipsilateral) fibers from the trigeminal nuclei. A topographical organization of trigeminocerebellar fibers is present. The mesencephalic tract nucleus projects to the anterior lobe, the simple lobule (HVI), lobules VI, VIII, and the dorsal paraflocculus. The ventral group of the princeps and spinal tract (mainly IDV) nuclei projects to all lobules studied in vermis and hemispheres. More dorsal parts of these nuclei have a more restricted projection field including the vermal lobules VI, VII, and IX and the hemisphere. Cells within and ventral to the motor nucleus of the trigeminal nerve were found labeled after injections into the anterior lobe, the simple lobule, and lobule IX. Labeled cells in the region of the nucleus ovalis and close to the solitary tract project to the simple and paramedian lobule and lobule IX.

An autoradiographic study of the projections of visual cortical area 1 to the thalamus, pretectum and superior colliculus of the rabbit.

The projections of visual cortical area 1 (vl) to the thalamus, pretectum and superior colliculus of the rabbit have been studied by Giolli and Guthrie ('67, '71) using the Nauta and Fink-Heimer methods to determine the course and distribution of degenerating nerve fibers. The present study represents a reinvestigation of these same projections utilizing the tracing method of autoradiography. An injection of 3H leucine was produced within a small region of vl in each of 18 adult albino rabbits, and the brains were subsequently processed for autoradiography by the method of Cowan et al. ('72). The results have confirmed the observations of Giolli and Guthrie ('67, '71) (1) by showing that vl of the rabbit projects to the thalamic reticular nucleus, the ventral lateral geniculate nucleus, the dorsal lateral geniculate nucleus; the pulvinar, the anterior and posterior pretectal nuclei and the superior colliculus and (2) by showing that a particular retinotopic organization is present in each of these projections. However, unlike Giolli and Guthrie ('67, '71), the present autoradiographic study has further revealed (1) that both the ventrolateral and the posterior thalamic nuclei receive inputs from vl and (2) that the nucleus of the optic tract is not innervated by axons originating from vl.

Distribution of neuropeptides in the infundibular nucleus of the sheep.

The distribution of neurons exhibiting somatostatin (SRIF)-, neuropeptide Y (NPY)-, beta-endorphin- and neurotensin (NT)-like immunoreactivity within the infundibular nucleus (NI) of the sheep, and the extent of coexistence of the above peptides within individual neurons of the NI were investigated with immunocytochemical techniques. Our results show that the above neurochemical types of neurons exhibit specific and largely non-overlapping patterns of distribution within the NI of the sheep. Furthermore, the coexistence of these peptides within neurons of the NI is very limited, as from all possible permutations checked, only SRIF and NPY were found together in a small number of cells.

Coexistence of neuropeptides in the hypothalamic paraventricular nucleus of the sheep.

The chemical organization of the hypothalamic paraventricular nucleus (NPV) of the sheep was studied immunocytochemically by using antisera raised against oxytocin (OXY), ovine corticotropin releasing factor (CRF), somatostatin (SRIF), neurotensin (NT) and vasoactive intestinal polypeptide (VIP). Examination of immunocytochemically stained frozen, 30-40 microns thick, and paraffin serial, 6 microns thick, sections has shown that chemically specified subsets of neurons are not strictly demarcated anatomically and that OXY and SRIF or CRF and VIP are jointly expressed by certain subpopulations of neurons which are different from that producing both OXY and CRF.

Cerebellar afferents from motor nuclei of cranial nerves, the nucleus of the solitary tract, and nuclei coeruleus and parabrachialis in sheep, demonstrated with retrograde transport of horseradish peroxidase.

Following HRP injections in the cerebellar cortex of the sheep (except the ventral part of the anterior lobe, the flocculus and ventral paraflocculus), labeled cells were evident in motor nuclei of cranial nerves(XII, VII, VI, III, visceromotor nucleus of X and nucleus ambiguus), in the solitary tract nucleus, the nucleus coeruleus and the parabrachial nucleus.

The coexistence of oxytocin and corticotropin-releasing factor in the hypothalamus: an immunocytochemical study in the rat, sheep and hedgehog.

The unlabeled antibody enzyme method has been applied on adjacent sections in order to investigate coexistence of oxytocin (OXY) and corticotropin-releasing factor (CRF) within individual neurons of the hypothalamic paraventricular nucleus of the colchicine-treated rat, sheep and hedgehog. Our results show that, although OXY and CRF immunoreactivities are both expressed by a number of cells in the rat and the sheep paraventricular nucleus, this is not the case for the hedgehog.

Basal forebrain neurons project to the cortical mantle of the European hedgehog (Erinaceus europaeus).

The basal forebrain projections to the cortical mantle of the hedgehog were traced using the WGA-HRP method. The nuclei of the vertical and horizontal limbs of the diagonal band of Broca, the nucleus basalis and the substantia innominata were found to project to the ipsilateral frontal, parietal and occipital cortices. These projections, apparently cholinergic, were not topographically organized.

Cerebellar cortical afferents from the dorsal column nuclei in sheep, demonstrated with retrograde transport of horseradish peroxidase.

Following horseradish peroxidase injections in the cortex of the sheep cerebellum (except the ventral part of the anterior lobe, the flocculus and ventral paraflocculus), labeled cells were found in nucleus gracilis, medial cuneate and lateral cuneate. The present findings provide evidence that the projection of the dorsal column nuclei to the cerebellum in the sheep is more extensive than has been reported for the common laboratory animals. Projections to the vermis are bilateral, projections to the hemisphere are mainly ipsilateral.

Retinal projections in the hedgehog (Erinaceus europaeus). An autoradiographic and horseradish peroxidase study.

The retinal projections of the hedgehog were studied using tritiated leucine and horseradish peroxidase as orthograde tracers. In both series of experiments labeling was seen bilaterally in the suprachiasmatic nucleus, the dorsal and the ventral lateral geniculate nucleus, the superior colliculus, and the pretectal area and contralaterally in the terminal nuclei (dorsal, lateral and medial) of the accessory optic system. A retino-intergeniculate leaflet projection is described for the first time in this species, and its significance is discussed.

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

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.

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

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 projections to the spinal cord are comparable to those described in other species.