EFFECTS OF HIBERNATION AND AROUSAL FROM HIBERNATION ON MESENTERIC ARTERIAL RESPONSES OF THE GOLDEN-HAMSTER

The aim of our study was to investigate the changes that occur in func tional responses of the golden hamster mesenteric arterial bed after: 1) 8 wk of hibernation and 2) 2 hr after arousal from hibernation. Age -matched and cold-exposed hamsters were used as controls. At 8 wk afte r hibernation there was an increase in sensitivity of vasoconstrictor responses to sympathetic nerve stimulation but no significant differen ce in constrictor responses to norepinephrine, alpha,beta-methylene AT P, uridine 5'-triphosphate or KCI (studied in unconstricted preparatio ns), or in endothelium-dependent vasodilatation to acetylcholine and u ridine 5'-triphosphate tin methoxamine-preconstricted preparations) co mpared with the control groups. In contrast, in the arousal from hiber nation group, sympathetic vasoconstriction was similar to that in the control groups, and the maximal response to exogenous norepinephrine, and responses to alpha,beta-methylene ATP were augmented. These result s suggest that there is an augmentation of sympathetic neurotransmissi on of golden hamster mesenteric arteries at 8 wk after hibernation, wh ich appears to be due to pre- rather than postjunctional changes. This is reversed with arousal from hibernation, when the sensitivity of sy mpathetic contractile responses is not different from that of the cont rols. However, an increase in maximal constrictor responses to norepin ephrine suggests that postjunctional changes may occur in sympathetic neurotransmission during arousal.