ENHANCED VASOCONSTRICTOR RESPONSES IN RENAL AND FEMORAL ARTERIES OF THE GOLDEN-HAMSTER DURING HIBERNATION

1. The present study assessed local regulation of vascular tone of eut hermic (control), cold control and hibernating golden hamsters. Sympat hetic neurotransmission in the renal artery, the long term effects of hibernation on perivascular nerve activity, and the responsiveness of femoral artery to a number of neurotransmitters and hormones with both constrictor and dilator actions during hibernation are described. 2. The contractile responses of the renal arterial rings to transmural ne rve stimulation (80 V, 0.1. ms, 4-64 Hz, for 1 s) were negligible in c ontrols, significantly increased at higher frequencies of stimulation in cold controls and markedly enhanced in the hibernating group at all frequencies tested. The contractile responses to exogenous noradrenal ine (NA; 0.1-100 mu M) were significantly increased in the renal arter ies of hibernating hamsters compared with controls, but not compared w ith cold controls. Responses to exogenous ATP (1-3000 mu M) and KCl (1 20 mM) were similar among all experimental groups. 3. The maximal cont ractile responses of femoral arterial rings to the sympathetic cotrans mitter ATP and 5-hydroxytryptamine were increased by approximately 124 % and 99%, respectively, in hibernating compared with cold control pre parations without a change in the concentration of agonist that produc es half-maximal response. However, the responses to NA were not altere d during hibernation.4. Vasoconstriction of femoral arterial rings in response to arginine vasopressin was significantly enhanced in both co ld controls and hibernating groups, while vasoconstriction in response to endothelin-1 and KCl was unaltered. 5. The dilator responses of fe moral arterial rings to acetylcholine, sodium nitroprusside and adenos ine were not different among the groups. 6. It is suggested that the m arked augmentation of sympathetic neurotransmission, selective superse nsitivity of the vascular smooth muscle to sympathetic contractile age nts and unaltered vasodilatory mechanisms may provide a means for main tenance of vascular tone and peripheral resistance during hibernation.