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.     

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.     

Afferent connections of the cat lateral vestibular nucleus

Location within the brain of HP-labeled neurons (origins of projections to the lateral vestibular nucleus) was investigated by iontophoretic injection of this enzyme. Bilateral projections to the following midbrain structures were revealed: the field of Forel, interstitial nuclei of Cajal, oculomotor nerve nuclei, and the red nucleus — to all parts of the lateral vestibular nucleus. Bilateral projections were also shown from more caudally located structures, viz. the superior, medial and inferior (descending) vestibular nuclei, Y groups of the vestibular nuclear complex, facial nucleus and hypoglossi, nucleus prepositus nervi hypoglossi and caudal nuclei of the trigeminal tract; ipsilateral projections from crus IIa of lobulus ansiformus of the cerebellar hemisphere; contralateral projections from the bulbar lateral reticular nucleus and Deiter's nucleus. A tonic organization pattern of afferent inputs from a number of brainstem formations to the dorsal and ventral lateral vestibular nucleus is revealed and trajectories of HP-labeled fiber systems projecting to Deiter's nucleus described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 4, pp. 494–503, July–August, 1988.     

Afferent connections to the abducent nucleus in the cat.

The afferent connections to the abducent nucleus in the cat were studied by means of retrograde transport of WGA-HRP after implantations of the tracer in crystalline form. Retrogradely labelled cells were found bilaterally in the medial and descending vestibular nuclei, mainly in their ventral and medial portions, in the rostral part of the ipsilateral gigantocellular reticular nucleus, in the medial part of the contralateral caudal pontine reticular nucleus and bilaterally in the oculomotor nucleus, mainly in its dorsolateral division. Some labelled cells were also found bilaterally in the mesencephalic reticular formation, the periaqueductal grey and the nucleus of the trapezoid body.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

Afferent connections of the ventral magnocellular section of the cat red nucleus

The location within the brain of labeled neurons giving rise to projections to the ventral magnocellular section of the red nucleus were investigated by means of microiontophoretically injected horseradish peroxidase. Projections were identified from many cortical, thalamic, and hypothalamic structures and from the head of the caudate nucleus, septum, globus pallidus, anterior commissure nucleus, central amygdalar nucleus, field of Forel, Zona incerta, and a number of brainstem structures. Findings in accordance with those found in the literature were obtained on projections to the red nucleus from the coronary and cruciate cortical sulci, the midbrain and dentate (lateral) cerebellar nuclei, subststantia nigra, nucleus gracilis, and the cuneate nucleus. Trajectories of retrogradely labeled fiber systems of the red nucleus are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 680–687, September–October, 1988.     

Projections from neurons of the medial terminal nucleus of the accessory optic tract to the caudate nucleus in the cat revealed by combining techniques of retrograde axonal transport and experimentally induced degeneration

Neurons of the medial terminal nucleus of the accessory optic tract receiving direct retinal inputs were shown to project to the heat and body of the caudate nucleus in the cat using techniques of retrograde horseradish peroxidase axonal transport and experimentally induced degeneration. These primarily ipsilateral projections are evenly distributed throughout the aforementioned areas of the nucleus. Neurons of the medial terminal nucleus forming synaptic connections with caudate nucleus cells are distinguished by their varied shapes and sizes, ranging from 20 × 10 to 37.5 × 18 µm and are located in both the ventral and dorsal subdivisions of the nucleus. The supposed functional significance of these projections for the regulation of muscle tonus tension is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 214–219, March–April, 1986.     

Afferent connections in the ventromedial hypothalamus of rats demonstrated by retrograde transport of horseradish peroxidase

Projections into rat ventromedial hypothalamus were studied with retrograde transport of horseradish peroxidase (HRP). Following injection of HRP into ventromedial hypothalamus, labeled neurons were found in cortical and medial amygdaloid nuclei, ipsilateral mediodorsalis thalamus (MD), dorsal raphe nucleus, and contralateral sensorimotor cortex. Futhermore, labeled axons that connect directly amygdala with hypothalamus (DAH) also were found.     

Structural-functional connections of the lemniscus system with the caudate nucleus in the cat

Afferent projections were studied of nuclei of the spinal cord dorsal columns to the caudate nuclei. Evoked potentials (EPs) were recorded in the caudate nuclei and the nuclei of dorsal columns of the spinal cord to stimulation of the forelimb against the background and after unilateral elimination of the medial lemniscus. After the section, the EPs in the recorded nuclei sharply intensified in response to stimulation of the forelimb, ipsilateral to the section. Degenerative changes were also shown by electron microscopy in axonal terminals in the caudate nuclei at the operated side. Conclusion is drawn that the caudate nuclei receive direct connections from the contralateral nuclei of the spinal cord dorsal columns, which probably, conduct mainly kinesthetic afferent influences.     

Intracortical connections between neuron groups in the somatosensory cortex studied by the retrograde horseradish peroxidase transport method in rats

Short corticocortical connections between specialized groups of neurons (so-called barrels) were studied in the somatosensory cortex. After microinjections of horseradish peroxidase into a definite "barrel" labeled neurons were found in nearby groups within a radius of up to 400 µ. Labeled neurons were located chiefly in cortical layers V and III; 90% of them were pyramidal cells. Intracortical connection of labeled neurons were 1.6 times more numerous than thalamocortical connections. It is postulated that connections between neighboring cortical neuron groups are effected through their output cells, i.e., through pyramidal neurons of layers V and III.     

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.     

Efferent connections of the caudate nucleus in cats

Structural and ultrastructural changes in the frontal areas of the cortex and in the region of the globus pallidus were investigated after local and extensive destruction of the caudate nucleus. It was shown by the Fink-Heimer method that after local injury to the caudate nucleus by means of electrodes implanted 2–16 months before electrolytic destruction, only a few degenerating fibers of medium and thin caliber were present. Extensive destruction of the caudate nucleus (without preimplantation of electrodes) was followed by massive degeneration of fibers of different caliber in the frontal area of the cortex. After local injury to the caudate nucleus numerous thin degenerating axons 0.5–0.6 µ in diameter and degenerating terminals were found in the region of the globus pallidus. Degenerative changes in the axo-dendritic and axo-somatic terminals followed the "dark" type of course. It is concluded that no considerable direct projections of neurons of the caudate nucleus are present in the cortex. Degenerating fibers of average caliber in frontal areas of the cortex after destruction of the caudate nucleus are evidently axons of thalamic neurons and not from cells of the damaged nucleus.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 2, pp. 165–171, March–April, 1975.     

Functions of retrograde axonal transport

Retrograde axonal transport conveys materials from axon to cell body. One function of this process is recycling of materials originally transported from cell body to axon. In motoneurons, 50% of fast-transported protein is returned. Reversal probably occurs mainly at nerve terminals and, for labeled proteins, is nonselective. Proteolysis is not required, although changes in tertiary protein structure may occur with a repackaging of molecules in organelles different from those in which they were anterograde-transported. A second function is transfer of information about axonal status and terminal environment. Premature reversal of transport adjacent to an axon injury may be a component of a signal that initiates cell body chromatolysis. Transport of target cell-derived molecules with trophic effects on the cell body is exemplified by nerve growth factor transport in neurons dependent on it, and is probably a widespread phenomenon in the developing nervous system. Disorders in retrograde transport or reversal occur in some experimental neuropathies, and certain viruses, as well as tetanus toxin, may gain access to the central nervous system by this route.     

Afferent connections of the adjoining nucleus with the amygdaloid body and dopaminergic mesencephalic structures of the cat brain

By means of the retrograde axonal transport of horseradish peroxidase and luminescent markers the data have been obtained on topical organization of projections of the basal nucleus of the amygdaloid body, of the ventral field of the operculum and of the substantia nigra nuclei to the adjoining nucleus. In the medial and lateral segments of the adjoining nucleus the terminal fields of these structures overlap and have collaterals in the nuclei of the striopallidum. The interaction of limbic and motor informations in the adjoining nucleus is discussed.     

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 and efferent connections of the sexually dimorphic medial preoptic nucleus of the male quail revealed by in vitro transport of DiI

The medial preoptic nucleus of the Japanese quail is a testosterone-sensitive structure that is involved in the control of male copulatory behavior. The full understanding of the role played by this nucleus in the control of reproduction requires the identification of its afferent and efferent connections. In order to identify neural circuits involved in the control of the medial preoptic nucleus, we used the lipophilic fluorescent tracer DiI implanted in aldheyde-fixed tissue. Different strategies of brain dissection and different implantation sites were used to establish and confirm afferent and efferent connections of the nucleus. Anterograde projections reached the tuberal hypothalamus, the area ventralis of Tsai, and the substantia grisea centralis. Dense networks of fluorescent fibers were also seen in several hypothalamic nuclei, such as the anterior medialis hypothalami, the paraventricularis magnocellularis, and the ventromedialis hypothalami. A major projection in the dorsal direction was also observed from the medial preoptic nucleus toward the nucleus septalis lateralis and medialis. Afferents to the nucleus were seen from all these regions. Implantation of DiI into the substantia grisea centralis also revealed massive bidirectional connections with a large number of more caudal mesencephalic and pontine structures. The substantia grisea centralis therefore appears to be an important center connecting anterior levels of the brain to brain-stem nuclei that may be involved in the control of male copulatory behavior.     

Analysis of spontaneous unit activity of the cat caudate nucleus

Spontaneous unit activity recorded extracellularly from the caudate nucleus in acute experiments on cats was analyzed. A graph of the sliding mean frequency, an interspike interval histogram, correlogram, intensity function, and histogram of correlation between adjacent intervals were plotted for the spontaneous activity of each neuron. The spontaneous activity of neurons of the caudate nucleus showed considerable variability in time and its mean frequency varied for different neurons from 0.5 to 20 spikes/sec. Depending on the temporal pattern of the spikes and also on the statistical indices, spontaneous unit activity in the caudate nucleus was conventionally divided into two types: single and grouped. A switch from one type of activity to the other was observed for the same neuron. On the basis of the data as a whole it is impossible to regard the spontaneous unit activity of the caudate nucleus as a simple random (Poissonian) spike train.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 369–376, July–August, 1977.