[Projections of the dorsal raphe nucleus and midbrain central gray substance to the cat limbic system]. / Proektsii dorsal'nogo iadra shva i tsentral'nogo serogo veshchestva srednego mozga na limbicheskie struktury u koshki.

Morphological organization of connections of ventro-lateral (nociceptive) and dorso-lateral (analgetic) midbrain central gray (vl SGC and dl SGC), as well as of dorsal raphe nucleus (analgetic zone, Rd), with different limbic structures, responsible for the formation of various emotional states, was studied in 26 cats. The methods of electrical destruction of brain areas were used that were followed by the light and electron microscopic study of degenerating fibers and synapses. Heterogeneity of connections of above mentioned formations with different limbic structures was demonstrated. Connections Rd and dl SGC with upstream limbic structures were found to be very similar in their organization and expression. Connections of vl SGC with the same structures were significantly different. It is suggested that similar (antinociceptive) function of dl SGC and Rd has determined the likeness of their connections. This, in combination with the heterogeneity of SGC in conduction of the pain and analgesia, supports the identification of two brain systems: nociceptive, conducting pain sensitivity, and antinociceptive, inhibiting its conduction. The nociceptive system includes the following structures: vl SGC, posterior and lateral hypothalamic nuclei, preoptic area. In the antinociceptive system two subsystems could be distinguished: midbrain units of these subsystems are localized in different structures (Rd and dl SGC), while the upstream ones are found in the same hypothalamic nuclei--ventromedial, dorsomedial, paraventricular. As far as septum, amigdala, hippocampus and cingular cortex are concerned, it was found impossible to refer them to any of these systems--either nociceptive or antinociceptive--basing solely on the findings of morphological studies because of approximately similar representation of axons of neurons in vl SGC, dl SGC, Rd in these structures.

Sources of cortical, hypothalamic and spinal serotonergic projections: topical organization within the nucleus raphe dorsalis.

Retrograde axonal transport of fluorescent tracers (primuline, FluoroGold and Nuclear Yellow) from the spinal cord, frontal cortex, lateral hypothalamus to various neuronal groups of the midbrain periventricular gray substance (periaqueductal gray matter) and to the dorsolateral pontine tegmentum in the rat has been studied. Two large groups of serotonin-containing neurons have been found to be localized in the dorsomedial region of the nucleus raphe dorsalis. They are sources of projections into the thoracic segments of the spinal cord. A part of these neurons gives divergent axon collaterals to the frontal cortex and to the spinal cord. Non-collateral projections of the dorsolateral pontine tegmental catecholaminergic neurons to the spinal cord and the frontal cortex have been revealed. The data obtained give support to the fact that antinociceptive effect of stimulation of the "pure analgesic zone" [Fardin et al. (1984) Brain Res. 306, 105-123.] of the midbrain periaqueductal gray matter may be due to direct involvement of the nucleus raphe dorsalis into a descending control over transmitting nociceptive stimuli at the spinal cord level. Neurotransmissive and neuroregulatory roles of separate cortical, hypothalamic and spinal serotonergic projections of the nucleus raphe dorsalis neurons are discussed.

[Sources of cortical, hypothalamic and spinal serotoninergic projections: topical organization in the dorsal Raphe nucleus]. / Istochniki kortikal'nykh, gipotalamicheskikh i spinal'nykh serotoninergicheskikh proektsii: topicheskaia organizatsiia v predelakh dorsal'nogo iadra shva.

Distribution of primuline, fast blue, fluoro-gold and nuclear yellow-labelled monoamine-containing cells in periventricular gray and dorsolateral tegmentum (including locus coeruleus) was studied in the rat after injection of these fluorochromes into the frontal cortex, hypothalamus and spinal cord. Combination of monoamine fluorescence method and retrograde cell-labelling was used. Two big groups of serotonin-positive cells projecting into the upper thoracic spinal segments were found in dorsomedial zone of the dorsal raphe. Part of these units also had divergent axon projections to the frontal cortex. Such cellular arrangement allows a supposition that analgetic effects of dorsal raphe stimulation can be partially based on the direct participation of this structure in the descending control at the spinal level. Neurones, sources of cortical projections are intermingled with the cells projecting to the hypothalamus but some topical differentiation can be distinguished. Neurotransmitter and neuroregulatory roles of separate cortical and hypothalamic projections of serotonin-containing neurons of the dorsal raphe cells is discussed.

[An organizational analysis of the neurons forming the descending cortico-hypothalamic pathways]. / Analiz organizatsii neironov, obrazuiushchikh niskhodiashchie kortiko-gipotalamicheskie puti.

Quantitative assessment of spatial organization of cortical neurons forming descending fibre systems and hypothalamic structures has been made using technique of retrograde axonal transport of horseradish peroxidase. Heterogeneity of cortico-hypothalamic bonds is determined: the prefrontal cortex exerts a more pronounced effect on the hypothalamus as compared with other cortical areas of the limbic brain. Cortico-hypothalamic neurons form neuronal groups on different frontal levels of the prefrontal cortex and convolution of the cingulum, a form and orientation of the group being determined by the topography of dominating axonal systems running to the hypothalamus. There are various forms of cell associations in the frames of neuronal populations. Ensemble groupings of neurons may underlie the principle of organization of direct cortico-hypothalamic ways.

[Associative connections of the parietal cortex in cats]. / Assotsiativnye sviazi temennoi kory golovnogo mozga koshki.

Cortico-cortical connections of sensory (visual, auditory and somatosensory) areas of cortex with parietal associative cortex were investigated in cat by means of retrograde axonal transport of horse-radish peroxidase and Fink-Haimer technique. The shape, size and localization of cells which make monosynaptic connections between the primary sensory areas and parietal cortex and the distribution of fiber terminals of such cells in the associative parietal cortex were determined. Maximum number of cells connected with field 7 of the parietal associative cortex was found in field V1 of the visual cortex, and with field 5 in field S1 of the somatosensory cortex. Besides HRP-positive pyramidal neurons, mainly localized in layers II-IV, labelled stellate and spindle-shaped cells were found in a small amount. The connections of parietal associative cortex are discussed on the basis of the data obtained.