Sources of direct afferents of the rostral field CA3 in the rat dorsal hippocampus

Afferents to the rostral field CA₃ of the dorsal hippocampus were investigated using horseradish peroxidase retrograde transport techniques. By iontophoretic injection of horseradish peroxidase into this area of the hippocampus cells stained with this enzyme could be identified in the anterior nuclei of the thalamus, the supramillary and submamillothalamic nuclei of the hypothalamus, and the midbrain central gray matter, as well as the parietal, insular, temporal, retrosplenial, and pyriform areas of the neocortex. The findings obtained complete the picture of connections between one of the least explored sections of the rat hippocampus and other brain structures.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 469–475, July–August, 1986.     

Study of afferent connections of the visual cortex in the ventral bank of the cruciate sulcus in cats by the method of retrograde axonal transport of horseradish peroxidase

To study the possible pathways along which visual signals reach a visual zone discovered by the writers in the cat frontal cortex in the ventral bank of the cruciate sulcus, horseradish peroxidase was injected into a site previously identified by physiological experiments. Stained neurons were discovered in visual areas of the cortex (lateral suprasylvian and ectosylvian), in the parietal cortex (areas 5 and 7), and also in small numbers in the prefrontal and limbic cortex. Stained neurons were found in the following nuclei in the thalamus: n. medialis dorsalis, intralaminar nuclei (nn. centralis lateralis, paracentralis, centralis medialis), nn. ventralis medialis, anteromedialis, and reuniens. Many stained neurons were found in the claustrum and a few in the substantia grisea centralis in the midbrain. The principal sources of inputs to the cortical area investigated are thus centers of the visual system or parts of the brain directly connected with it.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Brain Institute, All-Union Mental Health Research Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 43–49, January–February, 1985.     

Retrosplenial and hippocampal projections of structures of the thalamoparietal associative system in rats

Afferent connections of the nucleus lateralis posterior (NLP) of the thalamus and area 7 of the parietal cortex with the retrosplenial region of the limbic cortex and hippocampus were studied in rats with retrograde axon transport of horseradish peroxidase. It was shown that the NLP receives ipsilateral projections from area 29d neurons, while area 7 receives ipsilateral axons from area 29d and 29c neurons. It was found that associations of the retrosplenial region with associative cortex are far more pronounced than with associative thalamus. Moreover, the afferent connections of area 7 with area 29d are more numerous than with area 29c. We disclosed no projections of areas 29a and 29b to thalamoparietal system structures. In addition to neocortical input from the limbic cortex, area 7 receives afferent fibers from the archicortex; neurons situated in hippocampus area CA1 are the source of these projections.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy Academy of Sciences, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 647–655, November–December, 1991.     

Demonstration of afferent connections of the forebrain in Emys orbicularis turtles by the peroxidase method

The transport of horseradish peroxidase (HRP) out of the injection site in the dorsal ventricular ridge was studied in turtles Emys orbicularis. Labeled cells in the forebrain were observed in the paleostriatum among fibers of the lateral forebrain bundle. In the thalamus most of cells containing the granular HRP reaction product were located in the n. rotundus, n. reuniens and perirotundal nuclei (n. dorso-medialis anterior, n. magnocellularis thalami, n (centralis) lateralis, n. dorso-medialis). Fewer labeled cells were revealed in the n. anterior and n. ventralis. The density of labeled cells in the majority of all thalamic nuclei increased if the HRP was extended from the dorsal ventricular ridge into the neostriatum and the pallial thickening with adjacent general cortex. HRP positive cells in the pretectal area, nuclei of the posterior commissura and mesencephalic ventro-lateral tegmentum were observed only in cases when the enzyme was diffused from the injection site into the neostriatum, while the HRP retrograde transport to n. geniculatus lateralis, pars dorsalis was revealed only when HRP was extended into the pallial thickening and adjacent general cortex. Ascending connections of the paleostriatum, thalamic nuclei and mesencephalic tegmentum with telencephalic structures, mainly with the dorsal ventricular ridge, were discussed.     

Neurotensin-like immunoreactivity in the diencephalon of the adult male cat

Using an indirect immunoperoxidase technique, the location of neurotensin-like fibers and cell bodies was studied in the diencephalon of the cat. The findings showed that the hypothalamus is richer in neurotensin-like-immunoreactive structures than the thalamus, and that neurotensin-like-immunoreactive structures are more widely distributed in the hypothalamus than in the thalamus. A high density of immunoreactive fibers was observed in the hypothalamic regions, area hypothalamica dorsalis, hypothalamus posterior, nucleus (n.) filiformis and n. arcuatus, whereas a moderate density was found in the n. parafascicularis, n. paraventricularis anterior, hypothalamus lateralis, median eminence and n. paraventricularis hypothalami. Other diencephalic regions such as n. lateralis posterior, n. lateralis dorsalis, n. medialis dorsalis, n. habenularis lateralis, n. centrum medianum, n. rhomboidens, n. reuniens, hypothalamus anterior, n. supra chiasmaticus, hypothalamus ventromedialis, n. supraopticus and hypothalamus dorsomedialis had the lowest density of immunoreactive fibers. In addition, the densest clusters of neurotensin-like perikarya were found in the n. arcuatus, n. centralis medialis and hypothalamus posterior, whereas the n. medialis dorsalis, n. paraventricularis anterior, n. reuniens, hypothalamus lateralis and hypothalamus ventromedialis had the lowest density. In the n. lateralis dorsalis, n. supraopticus, area hypothalamica dorsalis and n. supra chiasmaticus the density of immunoreactive perikarya was moderate.     

Correlation between morphology and function in the rat hippocampus and hypothalamus

Correlation between morphology and function in the hippocampus and hypothalamus was studied by electrophysiological and morphological techniques. Single unit responses were recorded extracellularly in the arcuate and medial preoptic nuclei of the hypothalamus to application of single stimuli to the hippocampus. Phasic responses and primary inhibition predominated in the arcuate nucleus, whereas both phasic and tonic responses were observed in the medial preoptic nucleus. In the morphological experiments horseradish peroxidase was injected into the same region of the hippocampus. Stained cells were found in the nuclei of the mammillary body, mediobasal hypothalamus, and medial preoptic nucleus. Groups of stained neurons were discovered at the periphery of the ventro- and dorsomedial and also in the lateral and mammillary nuclei of the hypothalamus. Besides fusiform and triangular neurons, reticular neurons also were found in all structures except the medial mammillary nucleus. The results are discussed from the standpoint of interaction between hypothalamus and hippocampus.A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 427–434, September–October, 1979.     

Horseradish peroxidase-positive neurons of nonspecific thalamic nuclei projecting to the primary somatosensory cortex in cats

The morphology and topography of neurons whose axons form the nonspecific thalamic input in the primary somatosensory area were studied in the cat forebrain by the retrograde axonal horseradish peroxidase transport method. Stained cells were found in the dorsolateral part of the nucleus ventralis anterior, and were diffusely distributed in the nucleus centralis, lateralis, the lateral part of the nucleus dorsalis medialis, and the dorsal part of the centrum medianum. In the nucleus paracentralis only solitary, palely stained neurons were detected. Cells stained with horse-radish peroxidase were multipolar, triangular, or fusiform. The results are evidence that besides the ventrobasal complex, the nonspecific nuclei of the diencephalon also project into the somatosensory cortex. This indicates the existence of multiple afferent thalamic inputs into the somatic cortex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 435–440, September–October, 1979.     

Afferent brainstem projections to the hypothalmic locomotor region of the cat brain

The location of sources of direct projections to the hypothalamic locomotor region, electrical stimulation of which in the lightly anesthetized animal induced stepping along a moving treadmill, was studied by the retrograde axonal transport of horseradish peroxidase method in the cat brain stem. Different formations in the brain stem were shown to have direct connections with hypothalamic locomotor regions on both sides. Most sources of these afferent projections were located at sites of catecholamine- (nucl. reticularis lateralis, locus coeruleus, nucl. tractus solitarii) and serotonin-containing (nucl. raphe and substantia grisea centralis) neurons, parabrachial nuclei, and various sensory nuclei. Hypothalamic locomotor regions of both sides form bilateral connections.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 3, pp. 353–362, May–June, 1984.     

Direct connections of the hippocampus with the retrosplenial cortex in rats

Connections of the retrosplenial cortex with the hippocampus in rats were investigated by the method of retrograde axonal transport of horseradish peroxidase (HRP). If a crystal of HRP was introduced into the dorsocaudal part of the retrosplenial cortex, HRP-labeled cells were found in the rostral pole of hippocampal area CA₃ and in the presubiculum. After iontophoretic injection of HRP into the rostral pole of the hippocampus, HRP-labeled cells were found in layers V and VI of the retrosplenial cortex and in the presubiculum. The results are evidence of reciprocity of direct connections between the rostral pole of the hippocampus and the retrosplenial cortex, and also of the existence of direct efferents of the dorsal subiculum to the rostral pole of the hippocampus.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 102–107, January–February, 1985.     

Visual thalamic afferents to area 29 of the rat limbic cortex

Afferent connections of the retrosplenial area of the rat limbic cortex were investigated by the retrograde horseradish peroxidase axon transport method. After injection of horseradish peroxidase (HRP) into area 29 of the cortex, HRP-labeled cells were found in the dorsal part of the lateral geniculate body and the posterolateral, pretectal, and anterior dorsal thalamic nuclei. Connections were found between cortical area 29 and visual projection areas (areas 17 and 18a) and with area 29 on the contralateral side of the brain. The results are evidence that all the principal visual structures of the thalamus and the visual cortical projection area form direct projections to the retrosplenial cortex.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 135–139, March–April, 1982.     

Morphological and physiological study of afferent projections of the posterolateral thalamic nucleus in rats

It was shown by the method of retrograde axonal transport of horseradish peroxidase that the posterolateral thalamic nucleus (NPL) in rats receives considerable ascending projections from the superior colliculus (SC), the dorsal part of the lateral geniculate body (LGB), and the pretectal region (PT) and smaller projections from n. ventralis posterior (VP) and n. ventralis lateralis (VL) of the thalamus, the ventral part of LGB, the zona incerta, and anterior hypothalamus. The most marked descending projections run into NPL from area 18A of the cortex and the dentate fascia of the hippocampus, whereas inputs from cortical areas 18, 20, 7, 29c, 17, and 36 are less marked. In electrophysiological experiments with peripheral stimulation of visual, auditory, and somatosensory systems, polysensory convergence and interaction between signals from these systems were studied during isolated and simultaneous presentation of heterosensory stimuli. Of 229 neurons tested, 134 (58.5%) responded to at least one of the stimuli mentioned. Among monomodal neurons (53 of 134) there were some cells which responded to visual (77.4%) and somatic (22.6%) stimulation; neurons which responded only to acoustic stimulation were not found in the nucleus. As far as polymodal neurons (81 of 134) responding to two or three sensory stimuli are concerned, the most effective inputs of these units were visual and somatosensory. Interaction between stimuli acting on polymodal neurons was expressed as mutual inhibition or facilitation of responses; opposite effects could be observed on the various components of these responses.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 168–176, March–April, 1984.     

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.     

Differences in the sensory support of the anterior and posterior sections of the limbic cortex of the rat

Using retrograde axonal transport of horseradish peroxidase, studies have been made on the thalamic projections in the anterior and posterior parts of the limbic cortex with special reference to exterosensory system projections (visual, auditory and somatic). Projections of the retinorecipient nuclei of the anterior hypothalamus and classic thalamic visual relays (n. geniculatus lateralis dorsalis, n. lateralis posterior, pretectum) were found in the anterior and posterior limbic cortex. There are also inputs from the thalamic relays of the auditory (n. geniculatus medialis) and somatic (n. ventralis posterior) systems in the posterior limbic cortex The data obtained indicate: 1) that sensory supply of the limbic cortex in rats may be realized via direct pathways from sensory thalamic relays; 2) that thalamic sensory supply of the anterior limbic cortex differs from that of the posterior one. In the former, projections of the thalamic relays of the visual, auditory and somatic systems were found, whereas in the posterior cortex only visual system is presented. Topographic organization of the thalamic nuclear areas sending afferents to the anterior limbic cortex differs from that of the posterior limbic cortex.     

Connections linking the mamillary complex and hypothalamo-tegmental area of the brain with the brainstem in lizards

Connections between the hypothalamus and brainstem formations were investigated inOphisaurus apodus by locally injecting horseradish peroxidase (HP) or lectin-HP into the mamillary complex and the hypothalamo-tegmental area of the brain. Direct reciprocal connections were found linking mamillary complex nuclei and posterior and lateral hypothalamic structures with the following brainstem formations: central gray matter, parabrachial nucleus, raphe nuclei and the lateral loop, reticular formation of the caudal mesencephalon, pons, and medulla. It was concluded that direct bilateral hypothalamo-brainstem connections were already in place in reptiles, serving as the basis for sympatho-emotional nociceptive, and antinociceptive response.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 114–123, January–February, 1990.     

Investigating cerebellar connections in the turtle using the horseradish peroxidase technique of axonal transport

Cerebellar connections were investigated in the turtle using a technique of unilateral application of horseradish peroxidase to the body and the nuclei of the cerebellum as well as the structures of the mesencephalic tegmentum. Findings showed that the origins of projections to the cerebellum in the caudal sections of the brain (vestibular nuclei, perihypoglossal complex, inferior reticular formation with the inferior olive, the spinal chord, etc.) were more numerous than in the rostral mesodiencephalic regions, such as the tegmentum and the pretectum. Extensive efferent cerebellar projections were detected both in the medulla, including the vestibular nuclei and nuclei of the dorsal columns of the spinal cord, and in the mesencephalic tegmentum, but were rare in the hypothalamus and the ventral somatic section of the thalamus. The conclusion was reached that the closest similarity between reptiles and mammals is seen in the afferent and efferent connections linking the cerebellum with the spinal cord, the caudal sections of the brain stem, and the mesencephalic brain structures, which have a common involvement in the regulation of muscle tonus and the coordination of locomotor activity.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 786–794, November–December, 1985.     

Horseradish peroxidase study of connections of the hippocampal (mediodorsal) cortex ofOphisaurus apodus

Sources of afferent projections of the hippocampal (mediodorsal) cortex were detected in lizards (Ophisaurus apodus) by the retrograde horseradish peroxidase transport method. Labeled neurons after injection of the enzyme were most numerous in the anterior dorsolateral thalamic nucleus, mammillary body, superior nucleus raphe, dorsal cortex (ipsilaterally), and the hippocampal cortex of the contralateral hemisphere. Fewer neurons projecting into the hippocampal cortex were found in these same structures on the side opposite to that of the injection, and also in the ventromedial zone of the telencephalon (olfactory tubercle, the nucleus of Broca's diagonal band, and the nucleus accumbens), the preoptic region of the hypothalamus, and the ventrotegmental region of the midbrain. Endings of efferent fibers from the hippocampal cortex were found in the septum, thalamus, hypothalamus (mainly on the side of injection of the enzyme), and also in the hippocampal and dorsal cortex of both hemispheres. The results show that afferent and efferent connections of the lizard's hippocampal cortex are similar to those of mammals.     

Efferent connections of the centrum medianum of the cat thalamus revealed by autoradiography

Efferent connections of the centrum medianum and parafascicular nucleus of the thalamus (CM-Pf complex) in cats were studied by the method of anterograde axonal transport of tritiated amino acids followed by autoradiography. Projections from CM-Pf ascend to nuclei of the ventral group and nonspecific nuclei of the thalamus, preoptic, dorsal, lateral, and posterior areas of the hypothalamus, and also into the subthalamic region. Descending pathways are formed only by neurons of the caudomedial part of CM-Pf. They project into the pretectal region, superior colliculus, reticular formation, locus coeruleus, region of the ramus communicans, and substantia grisea centralis of the mesencephalon and pons, and also into the nuclei raphe, magnocellular reticular area, and inferior olivary nucleus of the medulla. In agreement with previous observations it was found that the caudomedial part of CM-Pf does not send direct projections into the cortex and striatum.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 224–230, March–April, 1984.     

Distribution of horseradish peroxidase-labeled neurons giving rise to descending fiber systems in the basal ganglia and hypothalamus in cats

The distribution of neurons giving rise to various descending fiber systems to brain-stem structures in the basal ganglia (including amygdaloid nuclei) and hypothalamus of the cat was studied by the retrograde axonal transport of horseradish peroxidase method. Neurons in the medial part of the central nucleus and of the magnocellular part of the basal nucleus of the amygdaloid group were shown to send axons to the dorsal hippocampus, substantia nigra, lateral part of the central gray matter, and the mesencephalalic reticular formation and also to the region of the locus coeruleus and the lateral medullary reticular formation at the level of the inferior olives. The predominant source of projections to the hypothalamus and brainstem structures is the central amygdaloid nucleus, which also sends projections to the nucleus of the tractus solitarius, the dorsal motor nucleus of the vagus nerve, and the superior cervical segments of the spinal cord. Uncrossed fiber systems descending from the basal ganglia terminate at the level of the pons, whereas uncrossed and crossed fiber systems descending from the dorsal and ventromedial hypothalamus can be traced into the spinal cord. The possible role of nuclei of the amygdaloid group, the hypothalamus, and their efferent projections in the regulation of somatic and vegetative functions and also of complex behavioral reactions is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 14–23, January–February, 1981.     

Connections between presumed diencephalic nuclei of the lizard limbic system using horseradish peroxidase axonal transport technique

Connections between the anterior thalamic and habenular nuclei were investigated in the lizard by administering horseradish peroxidase to these nuclei. They were shown to have overlapping locations of afferent sources, namely basotelencephalic structures, nuclei of anterior and hippocampal commissures, preoptic and lateral hypothalamic area, and superior raphe nucleus, as well as common projection zones, viz: the mamillary complex and the ventral tegmental area. Specific connections confined to individual nuclei were discovered, apart from those common to the nuclei: A reciprocal connection with the dorsolateral hypothalamic nucleus (for the anterior dorsolateral nucleus), a projection to the interpeduncular nucleus (for the habenular nucleus), and to the dorsal hypothalamic area (for the dorsomedial nucleus). No sources of afferent pathways to the anterior thalamic nuclei were found in the mamillary complex. All the thalamic nuclei studied, togetherwith their connections, are considered diencephalic relay links in pathways comparable with the dorsal (in the case of the habenular nuclei) and the ventral (with respect to the anterior thalamic nuclei) pathways of the mammalian limbic system.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 110–120, January–February, 1987.     

Distribution of parvalbumin-immunoreactivity in the rat thalamus using a monoclonal antibody

1. The distribution of parvalbumin cell bodies and fibers in the thalamus of the rat was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. The densest clusters of immunoreactive perikarya were observed in the nuclei ventralis posterior, reticularis, ventralis anterior and zona incerta, whereas the nuclei habenularis lateralis, lateralis posterior, lateralis, centralis lateralis and ventralis lateralis had the lowest density. In the nucleus geniculatum laterale ventralis, the density of parvalbumin cell bodies was intermediate. In all these thalamic nuclei, small, round or fusiform immunoreactive cells with short immunolabeled dendritic processes were observed. 2. The densest network of immunoreactive fibers was observed in the nuclei geniculatum laterale ventralis, reticularis and zona incerta. The nuclei geniculatum laterale dorsalis, ventralis posterior, medialis ventralis, ventralis anterior, anterior ventralis, anterior dorsalis and rhomboidens contained a moderate number of parvalbumin fibers, whereas the nuclei lateralis posterior, habenularis lateralis, parataenialis, centrum medianum, lateralis, centralis lateralis, ventralis lateralis, medialis dorsalis, anterior medialis, ventralis medialis and lateralis anterior had the lowest density of immunoreactive fibers. In addition, a large number of immunoreactive fibers was found in the lemniscus medialis and a scarce number in the stria medullaris. 3. No immunoreactive structure was observed in the nuclei habenularis medialis, paraventricularis, reuniens and geniculatum mediale. 4. Thus, perikarya and fibers containing parvalbumin are widely distributed throughout the thalamus of the rat, suggesting that parvalbumin might play a role, directly or indirectly, in limbic, visual and somatosensory mechanisms.