[Temperature and cardiotropic effects of kyotorphin and neokyotorphin in hibernating and nonhibernating animals].

Physiological effects of kiotorphyn (KT) and neokiotorphyn (NKT) has been reviewed. These peptides were isolated from the brain of hibernating ground squirrel Citellus undulates (CU) and assumed to be endogenous regulators of hibernation NKT does not alter the process of entering to hibernation, but induces arousal from the sleeping. KT administration in squirrel delays the rise of heart rate and body temperature associeated with awakening provoked in the middle but not at the final stage of hibernation bout. Neither KT nor NKT induce physiological effects in rats and mice under normal environmental conditions. In mice with induced hypothermia (17-18 degrees C) NKT accelerates restoration of body temperature, whereas KT induces progressive hypothermia. In addition, NKT modulates cardiotropic effects of nucleotides found in physiologically active fractions of hibernating squirrel tissues. NKT as well as KT modify sensitivity of cardiovascular system to adrenaline and AMP in rats one day after hypothermia.