Projection of the celiac plexus to the afferent centers demonstrated by the horseradish peroxidase retrograde transport method

Using the horseradish peroxidase (HP) retrograde method for ascertaining connections of the celiac plexus of the white rat with various afferent centers, HP-marked neurocytes have been revealed in caudal nodes of the vagus nerves and in spinal nodes at the Th4-L2 level. Negative results have been obtained at investigation of the cervical spinal nodes and intramural nodes in the cat ileocecal part. Similar data are obtained, when connections of the celiac plexus with the same area of the cat gut are investigated. Therefore, the problem on interrelations of the celiac plexus with the proper afferent centers of the diaphragmatic+ nerve and the second type cells of Dogel in the cat intramural ganglia is still disputable.     

Connections of brainstem respiratory nuclei studied by the retrograde horseradish peroxidase axon transport method

Intrabulbar connections of respiratory nuclei and the medullary reticular formation and also descending pathways from these structures in the spinal cord were studied by the retrograde horseradish peroxidase axonal transport method in cats. Neurons of the nucleus ambiguus and nucleus retroambigualis (ventral respiratory group) and of the ventrolateral part of the nucleus of the tractus solitarius (dorsal respiratory group) were shown to form direct two-way connections with each other and with the medial region of the medulla. Neurons of the pneumotaxic center send uncrossed axons to the nucleus ambiguus and to the medial medullary reticular formation. Neurons of the contralateral homonymous nucleus and neurons of the nucleus of the tractus solitarius are sources of projections of the locus coeruleus. A well developed system of direct connections was found between neurons of respiratory nuclei of the two halves of the brain. The possible role of these nuclear formations in genesis of the respiratory rhythm and regulation of the respiratory and other motor functions of the reticular formation is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 149–157, March–April, 1982.     

Afferent connections of cat facial nucleus; a study using retrograde axonal transport of horseradish peroxidase

Neuronal populations in the brainstem and spinal cord — the sources of fiber pathways to the facial nucleus — were investigated in adult cats by microiontophoretically injecting horseradish peroxidase into restricted areas of the facial nucleus. Projections were identified from thenucleus nervi hypoglossi, nucleus praepositus hypoglossi, nucleus raphe pallidus, nucleus intercalatus, medial nucleus of the solitary tract, dorsal motor nucleus of the vagus, neurons of genu of the facial nerve, ipsilateral red nucleus, and reticular formation of the midbrain to the facial nucleus. Projections from a number of other brain structures to the facial nucleus also received confirmation. A topographic map was drawn up, showing how brainstem and spinal cord afferents are distributed in the facial nucleus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 35–45, January–February, 1986.     

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

A well-developed descending efferent system of the caudate nucleus has been revealed by retrograde axonal transport of horseradish peroxidase. It consists of numerous projections into the thalamus. A topical differentiation of the connections between the caudate nucleus and the paleostriatum and substantia nigra was found. It was established that the main source of efferent connections of the caudate nucleus were small and medium-sized neurons. It was demonstrated that the subthalamic nucleus has a special role in the descending efferent system of the caudate nucleus. In addition to the direct connections into the caudate nucleus itself the subthalamic nucleus has direct connections with the main output structures of the caudate nucleus, the paleostriatum, and the substantia nigra. The concept that the descending and ascending connections are interlinked in the mammalian central nervous system is supported by the results of this investigation into the caudate nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 509–517, July–August, 1985.     

Olivary projections from the pretectal region in the cat studied with horseradish peroxidase and tritiated amino acids axonal transport

The organization of the projection from the pretectal region to the inferior olive in the cat was studied with autoradiographic and horseradish peroxidase (HRP) methods. After injections of HRP into the olive in six cats, cells were labeled ipsilaterally in the anterior pretectal nucleus (NPA), the posterior pretectal nucleus (NPP), the nucleus of the optic tract (NOT), and the dorsal terminal nucleus of the accessory optic tract (DTN). In three experiments, tritiated amino acids were injected into those parts of the pretectal region which contained labeled cells in the HRP experiments, and the projections to the olive were plotted. Both NPA and NPP projected to the rostral half of the dorsal accessory olive, the rostromedial margin of the ventral lamella, and the lateral part of the ventrolateral outgrowth. NOT projected to the caudal half of the dorsal cap, while DTN projected to both the dorsal cap and nucleus beta. The projections are entirely ipsilateral.     

Afferent projections from the brainstem to the area hypothalamica dorsalis: a horseradish peroxidase study in the cat

Experiments using the retrograde transport of horseradish peroxidase were performed in order to identify the cells of origin the ascending projections from different brainstem regions to the area hypothalamica dorsalis (aHd) in the cat. The afferent inputs to this area originate mainly from the midbrain and medulla oblongata regions. The main afferent source of the area hypothalamica dorsalis arises from the substantia grisea centralis, where a large number of labeled cells were observed bilaterally, although more abundant on the ipsilateral side. Substantial afferents reach the aHd from the nuclei vestibularis medialis and inferior and the formatio reticularis mesencephali. A modest number of peroxidase-labeled neurons were observed in the nuclei ruber, interpeduncularis, substantia nigra, reticularis gigantocellularis, vestibularis lateralis, cuneatus and gracilis. From the pons, the nucleus raphe magnus sends a weak projection to the aHd. These anatomical data suggest that such area could be involved in visceral, sexual, nociceptive somatosensorial, sleep-waking and motor mechanisms.     

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.     

Afferent projections to the locus coeruleus nucleus in the cat. Study by the horseradish peroxidase technic]

Using a retrograde tracer technique with horseradish peroxidase, we have revealed some afferent projections to the locus coeruleus complex from the contralateral pontine tegmentum, raphe nuclei, substantia nigra, nucleus of the solitory tract, dorsal motor nucleus of the vagus and other regions of the ponto-bulbar reticular formation as well as from hypothalamic and preoptic areas.     

Visual inputs to the dorsocaudal fastigial nucleus of the cat cerebellum. An experimental study using single unit recordings and horseradish peroxidase labelling

Visual afferents to the cat fastigial nucleus (FN) have been studied with single unit recordings and horseradish peroxidase techniques. A total of 158 cells responding to electrical stimulation of the optic chiasm (OCh) were extracellularly recorded from the dorsocaudal part of the FN. They were classified into three groups: type-1 cells (48%) which showed early suppression and late facilitation; type-2 cells (38%) which showed early facilitation and late suppression; type-3 cells (14%) which exhibited long lasting suppression with no signs of facilitation. Eight of 32 cells tested showed the same response patterns to photic stimulation as to electrical stimulation of the OCh. None of the cells responding to electrical and photic stimulation, however, were found in the rostral and ventral parts of the FN. Furthermore, 29 cells which responded to electrical stimulation of the OCh were tested for responses to moving pattern stimulation. Seven (4 type-2 cells and 3 type-3 cells) of the 29 cells showed clear modulation, reflecting the velocity component of a horizontally moving pattern. However, none of 13 type-1 cells tested exhibited apparent modulation in relation to movement of the pattern. In order to trace the possible pathways mediating visual signals to this part of the FN, the horseradish peroxidase (HRP) method was used. Injection of HRP into the caudal FN resulted in the labelling of many cells, predominantly in the medial (M) and the descending (D) vestibular nuclei and in lobules VI and VII of the cerebellar vermis. A series of experiments further indicated the presence of possible pathways propagating visual signals to the caudal FN. The main routes are: 1) via the nucleus of the optic tract (NOT)--the dorsal part of the medullary reticular formation--the M and the D vestibular nuclei--to the FN, and 2) via the superior colliculus--the pontine nuclei--vermal lobules VI and VII--to the FN. The different physiological response patterns of FN cells may indicate that several types of visual signals involved with visually guided movements impinge upon the dorsocaudal FN.     

Hypophysiotropic neurons in the goldfish hypothalamus demonstrated by retrograde transport of horseradish peroxidase

Summary The horseradish-peroxidase (HRP) technique was used to visualize the cell bodies of axons projecting to the goldfish pituitary. Following intravenous injections of HRP, HRP reaction products were observed in axons of the rostral pars distalis, proximal pars distalis, neurointermediate lobe, pituitary stalk and in axons coursing from the pituitary into the hypothalamus. HRP-labelled cells in the brain were localized in two regions only — the nucleus preopticus (NPO) pars magnocellularis and pars parvocellularis, and the nucleus lateralis tuberis (NLT) of the hypothalamus. These observations suggest that the NPO and NLT are the source of the neurosecretory innervation of the goldfish pituitary.     

Thalamic inputs to the motor cortex studied in cats by retrograde axonal horseradish peroxidase transport

Thalamic afferent inputs of the motor cortex (area 4) were studied in cats by retrograde axonal transport of horseradish peroxidase (HRP). The main concentration of HRP-labeled neurons was found in rostral zones of the relay nuclei (of the ventrolateral and ventrobasal complex). A few labeled neurons were found in the mediodorsal association nucleus, where their distribution is quite local. HRP-labeled neurons of nonspecific intralaminar nuclei, projecting into the motor cortex, are present only in single numbers and show no tendency toward grouping in any parts of these nuclei. The results are evidence that the motor cortex receives heterogeneous afferentation from various thalamic nuclei, and it is evidently this which guarantees the reliability of transmission of incoming information.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 250–255, March–April, 1985.     

The retrograde transport of horseradish peroxidase: problems in the interpretation of its ultrastructural aspects.

In this study we consider critically the use of HRP in research on the ultrastructure of the Central Nervous System. In fact, although controls make by optical microscope on semi-thin sections made us certain that some of the neurons were definitely marked with the enzyme, when the same specimen was observed by electron microscope, in no case was it possible for us to distinguish any particular aspect of the ultrastructural morphology of labelling within neurons.