[The effect of short peptides isolated from the brain of a hibernating suslik on the rat EEG and behavior].

The intracerebroventricular injection of the peptides kyotorphin (KT), newkyotorphin (NKT), and Aps-Tyr (BS) changed rat behaviour. There was an increase in the rate of exploratory reactions, rearing, grooming, stereotypic scratching movements, yawning, stretching, hiccupping, sneezing. Similar effects had been earlier observed in rats after administration of the fraction (F, 1-10 kD) from the brain of hibernating ground squirrels in which the studied peptides were found. The EEG effects depended on a peptide dose. As in the case of F injection, KT in the dose of 4 mcg suppressed the theta- and alpha-rhythms, KT injection in the dose of 8 mcg produced similar effect within the first minutes. Then it was substituted for an enhancement of the delta-, theta-, and alpha-rhythms while the beta-activity was suppressed. The effects of BS (4 mcg) and KT (mcg) were similar, however, increase in the BS dose to 8 mcg resulted in an enhancement of the beta-activity as in the case of F injection. The NKT effects also consisted in delta-enhancement and beta-suppression, but, in contrast to KT, the theta- and alpha-suppression was short-term, delayed and occurred only after the peptide injection in the dose of 8 mcg.