A combined horseradish peroxidase and Golgi study on the afferent connections of the ventrobasal complex of the thalamus in the cat

Summary Afferent connections to the ventrobasal complex (VB) of the thalamus were studied by means of retrograde transport of horseradish peroxidase (HRP) and by the Golgi-method. After HRP-injection into the VB, peroxidase-positive cells were observed contralaterally in the dorsal column nuclei (DCN), in the trigeminal nuclei and in the lateral cervical nucleus (LCN), and ipsilaterally in the somatosensory I (SI) and II (SII) cortical areas. Labeled cells of different shape and size were compared with neurons impregnated by the Golgi-technique. On the basis of HRP-labeling it is concluded that cells projecting to the VB are different in size and shape even within one region and that they correspond to the relay or efferent neurons observed in the Golgimaterial.     

NPY-, galanin-, VIP/PHI-, CGRP- and substance P-immunoreactive neuronal subpopulations in cat autonomic and sensory ganglia and their projections

Summary The neuronal subpopulations in the cat stellate, lower lumbar and sacral sympathetic ganglia were studied with regard to the cellular distribution of immunoreactivity to tyrosine hydroxylase (TH), acetylcholinesterase (AChE) and various neuronal peptides. Coexistence of neuropeptide Y (NPY)- and galanin (GAL)-like immunoreactivity (LI) was found in a high proportion of the neuronal cell bodies; these cells also contained immunoreactivity to TH, confirming their presumably noradrenergic nature. Some TH- and GAL-immunoreactive principal ganglion cells lacked NPY-LI. Two populations (scattered and clustered) of vasoactive intestinal polypeptide (VIP)- and peptide histidine isoleucine (PHI)-positive cell bodies were found in the sympathetic ganglia studied. The scattered VIP/PHI neurons also contained AChE-LI, calcitonin gene-related peptide (CGRP)-and, following culture, substance P (SP)-LI. The clustered type only contained AChE-LI. In the submandibular and sphenopalatine ganglia, neurons were AChE- and VIP/ PHI-immunoreactive but lacked CGRP- and SP-LI. Many GAL- and occasional TH-positive neurons were found in these ganglia. In the spinal ganglia, single NPY-immunoreactive sensory neuronal cells were observed, in addition to CGRP- and SP-positive neurons. The present results show that there are at least two populations of sympathetic cholinergic neurons in the cat. Retrograde tracing experiments indicate that the scattered type of cholinergic neurons contains four vasodilator peptides (VIP, PHI, CGRP, SP) and provides an important input to sweat glands, whereas the clustered type (containing VIP and PHI) mainly innervates blood vessels in muscles.     

A computational model of how an interaction between the thalamocortical and thalamic reticular neurons transforms the low-frequency oscillations of the globus pallidus

In Parkinson’s disease, neurons of the internal segment of the globus pallidus (GPi) display the low-frequency tremor-related oscillations. These oscillatory activities are transmitted to the thalamic relay nuclei. Computer models of the interacting thalamocortical (TC) and thalamic reticular (RE) neurons were used to explore how the TC-RE network processes the low-frequency oscillations of the GPi neurons. The simulation results show that, by an interaction between the TC and RE neurons, the TC-RE network transforms a low-frequency oscillatory activity of the GPi neurons to a higher frequency of oscillatory activity of the TC neurons (the superharmonic frequency transformation). In addition to the interaction between the TC and RE neurons, the low-threshold calcium current in the RE and TC neurons and the hyperpolarization-activated cation current (I _h) in the TC neurons have significant roles in the superharmonic frequency transformation property of the TC-RE network. The external globus pallidus (GPe) oscillatory activity, which is directly transmitted to the RE nucleus also displays a significant modulatory effect on the superharmonic frequency transformation property of the TC-RE network. Action Editor: John Rinzel     

Detailed organization of cerebello-olivary projections in the cat. An autoradiographic study

Several small injections of tritiated leucine were placed in regions of the cerebellar nuclei and sites of distribution in the olive were revealed by autoradiography. Different survival periods from a few hours to several days were utilized and high or low specific activity tracers were evaluated. A general pattern of distribution whereby the dentate, anterior and posterior interposed respectively project to principal, dorsal accessory and medial accessory olives was confirmed. Several new details of distributions from regions of the interposed and dentate nuclei to parts of the olivary subdivisions were demonstrated. The pattern of representations is complex and distributed in three dimensions. It is very precise and approximates a point to point representation. However, these projections which appear relatively dense do not represent the only link between the cerebellar nuclei and olive. With survival periods of a few hours, additional lighter projections distributed according to a different pattern can be revealed. A small ipsilateral projection was observed and it is suggested that it is made of collaterals of the crossed fibers.     

Motor cortex projections to the thalamus. An autoradiographic study in the cat

Adult cats received tritiated proline-leucine injections into the pericruciate cortex (areas 4 gamma and 3a) unilaterally and the projections to the thalamus were analyzed. Ipsilateral projections were found in the following nuclei, from rostral to caudal: ventral anterior, reticular, ventral lateral, central medial, paracentral, central lateral, ventral medial, mediodorsal, ventral posterolateral, ventral posteroinferior, centre median, parafascicular and posterior complex. In the contralateral hemithalamus sparse projections were found within the paracentral, central lateral and ventral medial nuclei.     

Single units activities in ventral posterior and posterior group thalamic nuclei during nociceptive and non nociceptive stimulations in the cat.

The purpose of this study was to define, in hyperventilated and unanesthetized cats, the role of the posterior thalamic nuclei in pain mechanisms. Unit activities of these structures were compared to those of the ventro-posterior nucleus during non-noxious (touch, brushing) and noxious stimulations (pinches and intra-arterial injections of bradykinin into the limbs). 135 cells with somatic inputs and clear peripheral excitatory receptive field were studied. The cells driven by noxious stimulations were located in the posterior group nuclei as anatomically defined by Rinvik. These units, preferentially excited from contralateral receptive fields, were localized in POm, POl, suprageniculate nuclei, the magnocellular division of the medial geniculate body (Mgmc) and the ventral part of the lateral posterior nucleus. At this level two groups of units were found: those driven only by noxious stimulations and those driven by both noxious and non-noxious stimulations. On contrast, cells recorded at the levels of the VPm and VPl were not activated by noxious stimuli. These results emphasize the role of the posterior thalamic nuclei in pain processing.     

Efferent projections from the lateral septal nucleus to the anterior hypothalamus in the rat: A study combining Phaseolus vulgaris-leucoagglutinin tracing with vasopressin immunocytochemistry

Summary The tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) was injected into the lateral septum of the rat at different rostrocaudal locations to study the efferent septal projections to the anterior hypothalamus. For spatial correlation of these septofugal elements with the vasopressinergic system a dual immunocytochemical technique was used (i) to demonstrate nerve fibers and their corresponding bouton-like structures labeled with the tracer, and (ii) to identify vasopressin in the same section. The hypothalamic paraventricular and supraoptic nuclei, the accessory hypothalamic magnocellular system, and the suprachiasmatic nucleus are recipients of PHA-L-labeled fibers from all parts of the lateral septum. Close appositions between (i) these axons and their varicosities, and (ii) vasopressin-immunoreactive perikarya and their processes, putatively indicating functional interrelationships, were observed in all these nuclear areas, especially in their neuropil formations.Abbreviations F fornix - OC optic chiasm - OT optic tract - PVN paraventricular nucleus - SCN suprachiasmatic nucleus - SON supraoptic nucleus - III third ventricle     

Immunochemical study of galanin in the cat digestive tract and autonomic ganglia

The presence of galanin was examined in the cat gut and related autonomic nervous structures using radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). In the gut wall, the concentration of galanin-like immunoreactivity (GAL-LI) was assayed separately in the muscular layers with the nervous plexuses and in the mucosa and ranged from 0.35 to 0.55 pmol/g wet tissue. In the autonomic nervous structures, GAL-LI concentrations ranged from 0.22 (thoracic spinal ganglia) to 0.81 (inferior mesenteric ganglion) pmol/g wet tissue. The presence of galanin was checked by HPLC in the antrum, intestine, and colon. HPLC of extractable material revealed a major peak coeluting with the synthetic porcine peptide and minor earlier peaks representing likely different molecular forms of galanin. Our study strengthens the notion that galanin acts in nervous control of the cat gut functions.     

Organization of the cortico-ponto-cerebellar pathway to the dorsal paraflocculus. An experimental study with anterograde and retrograde transport of WGA-HRP in the cat.

To reveal the organization and relative magnitude of connections from various parts of the cerebral cortex to the dorsal paraflocculus via the pontine nuclei, WGA-HRP was injected in the dorsal paraflocculus in conjunction with injection of the same tracer in various parts of the cerebral cortex in 17 cats. Termination areas of cortical fibres (anterogradely labelled) and pontine neurons projecting to the dorsal paraflocculus (retrogradely labelled) were carefully plotted in serial transverse sections. As an average of countings in ten cats, 90% of the labelled cells were found in the pontine nuclei contralateral to the injection, and the majority (70%) were located in the rostral half of the nuclei. The highest degree of overlap between anterograde and retrograde labelling was found after injections of the parietal association cortex (areas 5 and 7). In an experiment with double anterograde tracing, it was shown that both area 5 and 7 contribute substantially to the cerebral inputs to the dorsal paraflocculus. High degree of overlap also occurred after injections of several visual cortical areas (areas 17, 18, 19, 20 and the posteromedial lateral suprasylvian visual area, PMLS). Cases with injections restricted to individual visual areas indicate that they all contribute to the parafloccular input. Considerably less overlap occurred after injections of the primary sensorimotor region (SI, MI) and second somatosensory area (SII), while the supplementary motor area, the auditory cortex and gyrus cinguli probably have no or very restricted access to the dorsal paraflocculus. It is concluded that the dorsal paraflocculus has its major cortical input from the parietal association cortex and the visual cortical areas. Since all the various cortical regions studied project to largely different parts of the pontine nuclei, and overlap with neurons projecting to the dorsal paraflocculus takes place at numerous places, it follows that the pontine neurons projecting to the dorsal paraflocculus must consist of many subgroups differing with regard to their cortical input.     

The efferent connections of the lateral septal nucleus in the guinea pig: projections to the diencephalon and brainstem

Summary The anterograde Phaseolus vulgaris-leucoagglutinin (PHA-L) tracing technique was used to determine the distribution of efferent fibers originating in the lateral septal nucleus of the guinea pig. For complementary detection of the chemical identity of the target neurons, double-labeling immunocytochemistry was performed with antibodies to PHA-L and to vasopressin, oxytocin, vasoactive intestinal polypeptide, serotonin or dopamine -hydroxylase, respectively. The hypothalamus received the majority of the PHA-L-stained septofugal fibers. Here, a specific topography was observed. (1) The medial and lateral preoptic area, (2) the anterior, lateral, dorsal, posterior hypothalamic and retrochiasmatic area, (3) the supraoptic, paraventricular, suprachiasmatic, dorsomedial, caudal ventromedial and arcuate nuclei, and (4) the tuberomammillary, medial and lateral supramammillary, dorsal and ventral premammillary nuclei always contained PHA-L-labeled fibers. The rostral portion of the ventromedial nucleus and the medial and lateral mammillary nucleus only occasionally showed weak terminal labeling. In other diencephalic areas, termination of PHA-L-labeled fibers was observed in the epithalamus and the nuclei of the midline region of the thalamus. In the mesencephalon, terminal varicosities occurred in the ventral tegmental area, interfascicular and interpeduncular nucleus, and periaqueductal gray. In addition, the dorsal and medial raphe nuclei of the metencephalon, together with the locus coeruleus and the dorsal tegmental nucleus, received lateral septal efferents.     

Scanning electron-microscopic study of Reissner's fiber in the caudal spinal cord of the cat and rabbit

Summary The caudal portion of Reissner's fiber was examined by scanning electron microscopy (SEM) in the spinal cord of the cat and rabbit. In some preparations of both species the fiber displayed in the sinus terminalis of the central canal either stump-like terminations or structural modifications such as knot-like swellings and convolutions. In the same area homogeneous material could also be found, which obviously originated from the disintegrating fiber.     

Nervous connections of the parietal eye in adult Lacerta s. sicula Rafinesque as demonstrated by anterograde and retrograde transport of horseradish peroxidase

Summary Subsequent to the injection of horseradish peroxidase into the parietal eye of adult Lacerta sicula, the course of the parietal nerve and its projections were determined.The parietal nerve enters the left habenular ganglion where it branches into a medial and a lateral route. Some nerve fibers decussate within the habenular commissure. Whereas this pathway exhibits a striking asymmetry at the level of the habenular ganglia, its projections to the dorsolateral nucleus of the thalamus, the periventricular hypothalamic area, the preoptic hypothalamic and telencephalic regions, and the pretectal area are arranged in a strictly symmetric manner. A possible innervation of tegmental areas could not be proven due to the presence of endogenous peroxidase within these regions. No parietal nerve fibers were observed in the optic tectum.In a few animals investigated, scattered labeled perikarya were located in the periventricular hypothalamic gray indicating a parietopetal innervation in Lacerta sicula. The injection of horseradish peroxidase into one of the lateral eyes revealed terminal areas of the optic nerve within the preoptic region, and the thalamic and pretectal nuclei, displaying partial overlapping with the projections of the parietal nerve to these areas.From the present investigation further evidence is obtained that the pineal complex of lower vertebrates is a component of the photoneuroendocrine system. Particular emphasis is placed upon the nervous connections between the parietal eye and the hypothalamus, described for the first time in the present study.Supported by the Deutsche Forschungsgemeinschaft (Grant Ko 758/1)In partial fulfillment of the requirements of the degree of Dr. med., Faculty of Medicine, Justus Liebig University of Giessen     

Distributional pattern of serotonin-immunoreactive nerve fibers in the lateral geniculate nucleus of the rat,cat and monkey (Macaca fuscata)

Summary The distribution of serotonin-containing nerve fibers in the lateral geniculate nucleus (LGN) of the rat, cat, and monkey (Macaca fuscata) was studied by use of the peroxidase-antiperoxidase method and an antiserum against serotonin. In all three species, the pattern of fibers was denser in the ventral portion of the LGN (LGNv) than in the dorsal nuclear portion (LGNd). In the LGNd of rat, serotonin-immunoreactive fibers were evenly distributed in the form of a dense network, but in cat and monkey there were marked regional differences. Serotonin-immunoreactive elements were most numerous in the C complex and medial interlaminal nucleus of cat, and in the S layer and interlaminar zones of Macaca fuscata.Supported by a grant from the Ministry of Education, Science, and Culture of Japan (No. 57214028)     

An angiographic study of the carotid arterial and jugular venous systems in the cat.

Standard techniques for performing carotid angiography in dogs and in man were adapted to the cat in order to study the vascularization of both intracranial and extracranial structures. Venous drainage was examined by venography of selected vessels. The carotid-cerebral and the vertebral-basilar arterial systems of the cat were studied, although no attempt was made to define the territory supplied by each system. In serial angiograms, vascularization of the rete mirabile conjugatum was visualized and distinct arterial and venous retia were delineated. Large facial veins were seen approximately one second after the intra-arterial injection of radio-contrast material. The early filling of the large facial veins appeared to be the result of an artery-to-venous shunt. Contrast material flowed posteriorly in these veins and drained into the venous rete. When contrast material was injected either into the sagittal sinus or retrograde in the external jugular vein, the internal jugular vein was visible in four of ten cats. This vessel drained blood directly from intracranial contents before anastomosis with the vertebral and external jugular veins.     

The thalamic paraventricular nucleus relays information from the suprachiasmatic nucleus to the amygdala: A combined anterograde and retrograde tracing study in the rat at the light and electron microscopic levels

The relationship between efferents of the hypothalamic suprachiasmatic nucleus (SCN) and neurons of the thalamic paraventricular nucleus (PVT) projecting to the amygdala was investigated in the rat using tract tracing in light and electron microscopy. Biotinylated dextran amine was used to label anterogradely SCN efferents. These fibers were found to reach the thalamic midline, terminating in PVT, through three pathways: anterodorsally through the preoptic region, dorsally through the periventricular hypothalamus, and through the contralateral medial hypothalamic and preoptic areas after crossing the midline in the optic chiasm. Preterminal and terminal-like elements labeled from the SCN were distributed throughout the rostrocaudal extent of PVT, with an anteroposterior gradient of density. Labeled terminal elements were densest in the dorsal portion of PVT beneath the ependymal lining and some of them entered the ependyma. Anterograde tracing of SCN fibers was combined with injections of retrograde tracers in the amygdala. Numerous retrogradely labeled cell bodies were seen throughout PVT, with a prevalence in its anterodorsal portion. Overlap was detected between puncta labeled from the SCN and retrogradely labeled neurons, especially in the anterodorsal sector of PVT, where numerous puncta were in close apposition to thalamo-amygdaloid cells. Electron microscopy revealed that boutons labeled from the SCN established synaptic contacts with dendritic profiles of PVT neurons labeled from the amygdala. The findings demonstrate that information processed in the biological clock is conveyed to the amygdala through PVT, indicating that this nucleus plays a role in the transfer of circadian timing information to the limbic system.