Protein 70 kDa in the control of sleep and thermoregulation

Abstract

Studies of expression of molecular chaperones of the family of Heat Shock Proteins 70 kDa (HSP70) in the mouse and rat brain during sleep deprivation do not answer the question whether the HSP70 produce somnogenic effect. In the present work there are studied effects of exogenous Hsp70 that is known to be able to penetrate into living cells in vitro and to acquire properties of endogenous chaperone. Hsp70 was microinjected into the third brain ventricle of rats and pigeons at the beginning of the inactive period of the day when under natural conditions the sleep duration increases and the somato-visceral parameters decrease. Hsp70 was found to enhance this natural process and to produce an additional increase in the total time of slow-wave sleep, a more pronounced inhibition of the muscle contractive activity, and a deeper decrease in the brain temperature. A similarity in effects of Hsp70 in rats and pigeons was revealed. In both species the somnogenic effect of Hsp70 in is realized by activation of mechanisms of maintenance of in longer episodes of in slow-wave sleep. The hypothermic Hsp70 effect seems to be associated with a decrease in the muscle contractive activity level, rather than with an enhancement in peripheral vasodilation and with an increase of heat loss. A hypothesis is put forward that the neuroleptic effect of Hsp70 that includes the somnogenic, myorelaxing, and hypothermic effects is mediated by activation of GABAA receptors of the main inhibitory brain system.