EFFECTS OF HIBERNATION ON NEURAL AND ENDOTHELIAL CONTROL OF MESENTERIC-ARTERIES OF THE GOLDEN-HAMSTER

The effects of hibernation on mesenteric arterial innervation and func tion were examined using pharmacological and immunohistochemical techn iques in age-matched controls, cold-exposed controls, and 4-wk-hiberna ted golden hamsters. Electrical field stimulation of the isolated mese nteric arterial bed elicited frequency-dependent vasoconstriction. The sensitivity of responses was significantly increased in tissues from hibernating animals compared with cold-exposed controls. Vasoconstrict or responses to exogenous norepinephrine were also increased in hibern ation. However, there was a significant decrease in sensitivity of vas oconstriction to ATP in hibernated and cold-exposed tissue compared wi th age-matched controls. Ln preparations preconstricted with methoxami ne, endothelium-dependent vasodilator responses to acetylcholine and A TP were similar among the groups. Immunohistochemical investigation of mesenteric arteries revealed no differences among the groups in densi ty of innervation by nerves immunoreactive for tyrosine hydroxylase, n europeptide Y, and calcitonin gene-related peptide. Postjunctional cha nges appear to occur in hibernation, leading to augmentation of sympat hetic vasoconstriction, which is consistent with the increase in perip heral vascular resistance in hibernation. Endothelium-dependent vasodi latation is not significantly changed in hibernation in the hamster me senteric arterial bed.