Dynamics of characteristics of electrical activity recorded from tropho-and ergotropic zones of the rat hypothalamus in long-term emotional stress

We examined the dynamics of the spectral powers and indices of frequency components of background field electrical activity recorded from tropho-and ergotropic zones of the rat hypothalamus (electrohypothalamogram, EHtG) in the course of long-term (21 weeks) emotional stress induced by a zooconflict situation. Low-frequency delta-range (0.5 to 3.5 Hz) oscillations dominated in EHtGs recorded from both hypothalamic zones of both control and stressed animals. The integral power of EHtG oscillations underwent significant changes within the observation period; it considerably increased on the 6th to 9th week, dropped within the 12th to 18th week, and, after this (up to the 21st week) again increased, i.e., the dynamics, in general, were threephase. The dynamics of the power of separate frequency components of EHtG showed certain similarities to the dynamics of the integral power. Changes in the EHtG power in stressed animals were characterized by a shorter duration and greater rate; the powers of all EHtG components in these animals were lower than in control ones within a greater part of the observation period. The dynamics of the normalized powers and of the indices of different EHtG rhythms in stressed and control animals, especially the dynamics of dominating oscillations of the delta and theta ranges, were to a certain extent opposite. Our data show that changes in the EHtG can be electrographic correlates of subsequent phases of a long-lasting stress reaction of the organism in the course of the experiment; specific features of manifestation of these modifications in the tropho-and ergotropic hypothalamic zones are related to a certain specificity of the hormonal/transmitter mechanisms in the structures under study. Neirofiziologiya/Neurophysiology, Vol. 39, No. 1, pp. 69–80, January–February, 2007.