Expression of the c-Fos gene in the rat hypothalamus in electrical pain stimulation and UHF stimulation of the skin.

Studies of the pattern of activation of hypothalamic cells in conditions of electrical pain stimulation demonstrated an increase in the proportion of c-Fos-positive cells (to 72.02-98.95%), predominantly affecting cells of size 10-50 microm2. UHF irradiation of the skin activated hypothalamic cells of size 10-70 microm2 in the paraventricular and dorsomedial nuclei and in the periforniceal zone of the lateral hypothalamic field. Combined action of UHF irradiation of the skin and electrical pain stimulation led to decreases in the proportions of cells activated as a result of pain stimulation in the anterior hypothalamic field, the ventromedial nucleus, and the basal part of the lateral hypothalamic field. Changes in the distribution of activated cells by size (mainly a reduction in the proportion of cells of area 10-30 microm2 and an increase in the proportion of larger cells) were detected in the ventromedial nucleus and the basal part of the lateral field. UHF irradiation of the skin was found to have a modifying effect, consisting of a reduction in the degree of activation of hypothalamic cells evoked by electrical pain stimulation.