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Background impulse activity of the neurons of ipsilateral medial vestibular nucleus of unilaterally delabyrinthined rats was studied on different days after operation as well as after 5-day vibration. It was found that in intact animals mean neuron discharge rate is 16.6+/-1.7 Hz. On day 2 after affection it falls to 14.7+/-0.9 Hz and returns to the baseline on day 7 after surgery (16.6+/-1.2 Hz). Vibration impact raises mean impulse frequency to 21.2+/-2.8 Hz. Characteristics and significance of the results obtained are discussed.

The method of computer analyses was used for the research of the spectral changes of spontaneous neuronal activity of the medial vestibular nucleus ander vibration action (5, 10 and 15 daily). On the basis of neurons activity analyses it is possible to conclude that the majority of investigated units of flow and instability figured on different levels. The findings are discussed in respect to special points of functional meaning.

Effects of single, double, and rhythmic stimulation upon hypothalamic neurons responding to the 1st excitatory phase of lateral vestibular nucleus stimulation, were studied. The data obtained show that activation of some hypothalamic neurons following stimulation of the lateral vestibular nucleus has a monosynaptic character. The findings suggest that ascending afferents from the lateral vestibular nucleus to the hypothalamus pass via oligo- as well as polysynaptic pathways.

In acute experiments in rabbits the influence of stimulation of the ventromedial hypothalamic nucleus on the activity of neurons of vestibular Deiters' nucleus was studied under conditions of 15-day exposure to vibration (60 Hz, 0.8 mm, 3 h daily). The mechanisms are discussed which underlie the observed phenomena.

Responses of single units of anterior, ventromedial, lateral and posterior hypothalamus to stimulation of the caudal viscero-receptive region of nucleus tractus solitarius were recorded in anesthetized and immobilized cats. The patterns of the responses were mainly excitatory in all structures under study. The highest degree of reactivity was found for units in the lateral and posterior hypothalamus. According to the latency of the evoked discharges three types of responses were revealed: short (6-12 msec), middle (13-22 msec) and long-latency (22-60 msec) responses. At relatively low frequencies of stimulation the reproducibility was rather poor. Possible projections from nucleus tractus solitarius to the hypothalamus are discussed.

In anesthetized and immobilized cats, intact and with cut splanchnic nerves ("vagal" animals) of vagal nerves ("splanchnic" animals), high degree of responsiveness of hypothalamic neurons, with prevailing excitatory reactions, was found. The responses were obtained mainly to stimulation of gastric adapting mechanoreceptors. Information from the latters reaches the hypothalamic neurons through splanchnic and vagal afferents. Some hypothalamic mechanosensitive neurons were shown to be gluco- and osmosensitive and thereupon able to integrate both the neural and the humoral informations. The functional role of vagal and splanchnic mechanoreceptors of the stomach in activation of hypothalamic units and the "converging ability" of "visceral" neurons of the ventromedial hypothalamic feeding center, is discussed.

Responses of single units of posterior, anterior, ventromedial and lateral hypothalamus to stimulation of abdominal trunk of the vagus nerve were recorded in anesthetized cats simultaneously with the action potentials of the cervical region of the vagus nerve. 28.1% of the neurons responded to the stimulation, the pattern of responses being mainly excitatory. Vagal stimulation proved to be more effective for units of the lateral hypothalamus, 47.1% of the excitatory reactions followed stimulation of A gamma delta--B afferents and 40.4%--stimulation of C afferents of the vagus. Topical organization of the projection of these groups of visceral afferents to different regions of the hypothalamus was partially revealed. Responses of some A gamma sigma--B and C neurons to stimulation of vagus and sciatic nerves suggest convergence of visceral and somatic afferents to the "convergence" types of neurons. Some A gamma delta--B and C units, chiefly in the ventromedial hypothalamus, responded only to stimulation of visceral vagal afferents. The sensory properties of "visceral" neurons of the hypothalamus are discussed.

Under chloralose narcosis, employing the evoked potentials method, studies have been made on the projection of the posterior hypothalamus to the frontal cortex in 1-30 days old kittens. The animals were divided into 3 age groups: 1-9, 10-19 and 20-30 days. Studies of the EPs in different points of pericruciate zone showed that these potentials are observed in all the investigated points from the first days of postnatal life. The latent period of responses in the youngest animals varied from 40 to 80 ms, exhibiting insignificant fluctuations depending on the cortical zone investigated. From the very beginning of postnatal life, in the same cortical zone the EPs may be observed in response to stimulation of the ischiadic nerve as well. In older animals, the latent period of the EPs decreases in all the points, the decrease being most significant near the crucial fissure. To the 30th day of postnatal life, the EPs in this zone with respect to their latency and configuration became quite similar to those in adult animals. In the third age period, the latency varies from 6 to 10 ms in the focus of maximum activity; with the removal of the recording electrode from this zone the latent period of the hypothalamo-cortical responses increases up to 30-40 ms. Overlapping of the EPs in response to central and peripheral stimulation was observed at all age periods.