[Ultramicroscopic organization of the vascular plexus in the rabbit cerebral lateral ventricles and its changes under the effect of pyrogens]. / Ul'tramikroskopicheskaia organizatsiia sosudistogo spleteniia bokovykh zheludochkov mozga krolika i ee izmeneniia pri deistvii pirogenov.

By means of electron microscopical methods organization of various components of the vascular plexus in the rabbit cerebral lateral ventricles--ependymal and supraependymal cells, as well as capillaries, making the base of the hemato-encephalic and hemato-liquor barriers of the plexus have been studied. Injection of bacterial pyrogen (pyrogenal) to the animals is accompanied with an increasing permeability in the barriers of the vascular plexus for certain blood cells (lymphocytes, monocytes), their activation and transformation into plasma cells and macrophages. Under pyrogenal effect in the ventricle cavities activation of the supraependymal cells and intensification of their interaction with the underlying ependyma take place. In the ependymal layer local dilatation of intercellular spaces and intensification of exocytic processes are observed. The changes revealed demonstrate an active reaction of some elements of the vascular plexus to fever, dependent on injection of the bacterial pyrogens into the organism.

[Ultrastructural organization of the hypothalamic medial preoptic area and its changes under the effect of pyrogens]. / Ul'trastrukturnaia organizatsiia medial'noi preopticheskoi oblasti gipotalamusa i ee izmeneniia pri deistvii pirogenov.

In order to study structural bases of central mechanisms of thermoregulation, a comparative electron microscopic analysis of various cellular groups in one of thermosensitive zones of the cat hypothalamic area--the medial preoptic area--have been carried out under conditions of experimental fever. The latter is produced by injection of pyrogen of bacterial origin--pyrogenal--to the animals. Pyrogenal, increasing the body temperature, produces a stimulatory effect on various cellular elements, first of all on leucocytes, monocytes and macrophages in the medial preoptic area, as well as on endotheliocytes of the terminal vessels. Under pyrogenal effect activation of microglial cells and pericytes also takes place, and as a result of the rearrangements, occurring in the structure, they change into macrophages. This is an evidence of their active participation in the immune protection of the brain. According to the data from other investigations, all these activated cells produce peptide interleukin-1, one of the mediators of fever and stimulator of the immune system. Pyrogenal is stated to produce a stimulating effect on the astroglia and on some neurons of the medial preoptic area, that respond with cytoplasm increase and accumulation of numerous organelles. The reactive changes at fever in some neurons of the medial preoptic area can demonstrate that they belong to the thermosensitive pool. A conclusion is made, concerning a complex effect of pyrogenal, that results in a cooperative response of a number of cellular systems of the organism.

[Temperature dependence of neuronal activity in hypothalamic and hippocampal slices of the guinea-pig]. / Zavisimost' aktivnosti neironov ot temperatury v srezakh gipotalamusa i gippokampa morskoi svinki.

Unit activity in slices of the hippocampus and medial preoptic area of the hypothalamus of guinea-pigs was extracellularly recorded under conditions of temperature changes. Seven out of nineteen hypothalamic neurons showed changes in the firing rate at threshold temperatures of 36-38 degrees C. In the suprathreshold range the activity of these neurons depended on the temperature level. It is suggested that such neurons may form a sensory part of the system controlling brain temperature within a narrow (1-2 degrees C) range. The pyramidal layer cells of the control structure (hippocampus) were insensitive to the temperature level within 32-40 degrees C.

[Intrahypothalamic connections of the lateral hypothalamus]. / Vnutrigipotalamicheskie sviazi lateral'nogo gipotalamusa.

Using the axon degeneration method by R. Fink and L. Heimer, organization of intrathalamic connections between various areas of the lateral hypothalamus have been studied after unisided electrolitic lesion. At any location of the injury foci, similar patterns are observed in ipsilateral distribution of degenerating fibers along the whole lateral preoptico-hypothalamic area. The most massive degeneration is observed in the zone where the medial forebrain bundle (MFB) fibers run. The degenerating fibers spread forward--into the septal area, and backward--into the mesencephalic part of the brain. The rostral and caudal parts of the lateral hypothalamus, taking part in formation of the MFB collateralies towards the thalamus, are connected with various thalamic nuclei. Massive preterminal degeneration in the perifornical zone and single argerophile granules in the medial hypothalamus convincingly demonstrate an important role of the intermediate zone for connections of its medial and lateral parts with each other. The conclusion that the intrahypothalamic connections of the lateral hypothalamus are realized within the MFB system supports the modern notion on a close connection of the lateral hypothalamus with the system of longitudinal diffuse bundles of fibers of the medial anterocerebral pathway that run through it.

[Significance of theta-rhythm phases for excitatory transmission in the cerebral cortex]. / O znachenii faz teta-ritma dlia peredachi vozbuzhdeniia v kore golovnogo mozga.

The dependence of the number of motor reactions on the phase of theta-rhythm in the cerebral cortex, during which photic stimuli were presented was studied on unanaesthetized rabbits. Single flashes were presented to animals with 1--15 min intervals when theta-rhythm was dominant in the visual cortex. Each experimental session included 10--45 photic stimuli. It was found that the probability of rabbit's motor reaction to a photic stimulus depends on the phase of the theta-rhythm with which it coincides. The onset of a motor reaction to light in the majority of cases coincided with the positive phase of the theta-rhythm, which seems to be an optimal condition for the transmission of excitation in the cortex. The number of movements in response to light increases when the amplitude of the positive theta-rhythm oscillation is greater than the negative one. Recurrent inhibition in neural systems of the cerebral cortex seems to limit irradiation of excitation in case of big theta-rhythm amplitudes.

[Neuronal organization of the thermosensory region of the anterior hypothalamus]. / O neironal'noi organizatsii termosensornoi oblasti perednego gipotalamusa

In anesthetized rabbits, extracellular recording of activity of 236 neurons was made in the anterior hypothalamus on changing of its temperature (+/-3 degrees C). 27% of the neurons revealed high sensitivity to the temperature stimulus with coefficient Q10 from 2.4 to 30; 6% of the neurons reacted by the on-response type; 5% of the neurons changed their activity and preserved the new level. The character of the unit responses seems to indicate that the anterior hypothalamus fulfills not only the reception of temperature shifts, i.e. the primary processing of information, but its further analysis as well.

[The effect of leukocyte pyrogen on thermosensitive neurons of the anterior hypothalamus]. / Vliianie leikotsitarnogo pirogena na termochuvstvitel'nye neirony perednego gipotalamusa

Impulse activity of neurons of the medial preoptic and septal brain areas of rabbits caused by variations in the local temperature and systemic injections of the leukocytic and bacterial pyrogens was studied. The firing rate of the warmsensitive neurons decreased and that of the cold thermodetectors was activated as a result of pyrogen action. As compared with the bacterial pyrogen, leukocytic pyrogen caused a more rapid decrease of the warmthermodetector activity. Thermoneutral neurons failed to react considerably either to the leukocytic or to the bacterial pyrogen.