Biomedical subjects
Publications and source records attributed to L P Dymnikova.
Skin temperature of the rabbit back and face was increased to 38-40 degrees C or decreased to 22-26 degrees C. Out of 48 units under study 10 neurons responded to the cold skin stimulation, the latency of the responses varying from 10 to 50 s. The thalamic neurons responded also to the light, sound and mechanical stimuli.
The specific features of responses to thermal stimulation of the skin in neurons of the thermoregulation centre in the anterior and posterior hypothalamus were investigated in rabbits. Separate neurons were found to respond to temperature changes like skin thermoreceptors. A part of thermal signals from the skin is supposed to arrive to the thermoregulation centre without specific transformation.
The blood temperature in the main venous vessels reflects the formation of the heat balance in the body. In the rabbit posterior vena cava, the temperature increased by 0.19 degrees C-0.26 degrees C after confluence of the kidney and liver veins and decreased by 0.20 degrees C after confluence of the lumbal veins collecting the venous blood from the back muscles and skin vessels. The venous blood temperature in the right auricle was equal to blood temperature in the abdominal artery. When the ambient temperature changed from 22 degrees C-24 degrees C to 35 degrees C-40 degrees C, the temperature in the posterior vena cava and abdominal artery decreased by 0.25 degrees C-0.35 degrees C.
In thermoneutral ambient temperature, posterior hypothalamic neurons were found whose firing rate oscillations were associated with the hypothalamus and skin temperature fluctuations in unanesthetized rabbits. These neurons seem to take part in the thermoregulation function.
In unanesthetized rabbits, arterial (abdominal artery) and venous (v. posterior cava) temperatures were recorded. The arterio-venous temperature differences attained: 0.03 degrees against 0.18 degrees C, resp. (in neutral conditions) and 0.1 degrees against 0.3 degrees C (in cold and warm environments). The findings suggest a constancy and effectiveness of the internal heat exchange.
The temperature of arterial blood flowing to the ear and of venous blood outflowing from the latter was measured initially and under heat load in anesthetized rabbits. The partial calorimeter yielded the values of heat production from the ear (in cal/min). Heating of the animal increased the blood flow and the heat production (4- and 5-fold, resp.), the arterio venous difference remaining practically unaltered (0.8-0.9 degrees C).
Impulse activity of the posterior hypothalamic neurons was investigated under conditions of thermoneutral environment and at thermal skin stimulation of unanesthetized rabbits. Different types of the activity were classified. The responses of neurons to thermal stimulation were followed by changes in the activity types. Statistical criteria of these reactions were demonstrated.
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Changes in the mean firing rates of the preoptic and septal neurons under thermal stimulation of different skin areas were studied in unanesthetized rabbits. The skin temperature of the rabbit back (skin area I) or face (skin area II) was increased to 38-40 degrees C or decreased to 22-26 degrees C. Out of 111 units under study 21 units responded to changes in the skin temperature. All thermosensitive hypothalamic neurons responded to thermal stimulation of both skin areas. Different types of neuronal responses are described.
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Distribution of the intervals between spikes of 50 neurons in the posterior hypothalamus were studied in 17 unanesthetized rabbits. Three main types of the interspike-interval distribution were found in the thermoneutral zone: 1) unimodal, mode 2-4 ms; 2) unimodal, mode 16-512 ms; 3) bimodal, modes 2-10 ms and 64-512 ms (the posterior hypothalamus temperature was 39.1 +/- 0.02 degrees C). When the posterior hypothalamus temperature was increased or decreased (by 0.5-1.5 degrees C), changes in the initial interspike-interval distributions were observed in 11 neurons. The changes disappeared when the thermal stimuli were removed; 6 neurons (of 11) altered the mean firing rates too when the posterior hypothalamus temperature was changed.
Changes of the mean firing rate of neurons in the posterior hypothalamus on a regional increase or decrease in the midbrain temperature (0.6-2.0 degrees C) and skin temperature (3-5 degrees C) were studied in unanesthetized rabbits. In the posterior hypothalamus, neurons were found which responded both to the midbrain and skin temperature changes. The data suggest that the posterior hypothalamus takes part in the integration of signals from different central and peripheral temperature sensitive agents.
Changes in the mean firing rate of neurons in the posterior hypothalamus were studied in unanesthetized rabbits at the local increase in the brain temperature (0.7-1.5 C) and at an increase in the skin temperature (3-5 degrees C). 85 neurons were examined in 14 rabbits. 11 neurons (of 85) responded selectively to one of the used temperature influences. Changes in the unit activity to both temperature influences (more often of the same direction) were observed in 16 neurons. Different types of these neuronal responces were found. An increase in thermosensitivy was found in some neurons when the thermal stimulation of the skin was intensified.
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