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 functional 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 after hibernation there was an increase in sensitivity of vasoconstrictor responses to sympathetic nerve stimulation but no significant difference in constrictor responses to norepinephrine, alpha,beta-methylene ATP, uridine 5'-triphosphate or KCl (studied in unconstricted preparations), or in endothelium-dependent vasodilatation to acetylcholine and uridine 5'-triphosphate (in methoxamine-preconstricted preparations) compared with the control groups. In contrast, in the arousal from hibernation 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 results suggest that there is an augmentation of sympathetic neurotransmission of golden hamster mesenteric arteries at 8 wk after hibernation, which appears to be due to pre- rather than postjunctional changes. This is reversed with arousal from hibernation, when the sensitivity of sympathetic contractile responses is not different from that of the controls. However, an increase in maximal constrictor responses to norepinephrine suggests that postjunctional changes may occur in sympathetic neurotransmission during arousal.