[The effect of epiphyseal peptides on the dynamics of the circadian and minute motor biorhythms in rats].

Chronic administration of pineal peptide drug epitalamin (0.5 mg/kg for 5 to 10 days) modulated the rat circadian locomotor activity: the animals with low circadian rhythm amplitude were activated whereas the rats with an obvious circadian fluctuations were depressed. The epitalamine obviously decreased an apomorphine-induced stereotype at 13.00 hours rather than at 19.00 hours. The rhythmicity of the stereotype changed in different ways depending on the rat individual susceptibility. The drug decreased the number of 1-3-minute waves if it had been high initially, and increased it if slow fluctuations had dominated. Pineal peptides seem to participate in the maintenance of homeostatic equilibrium at the expense of stabilizing different periods of rhythmical processes.