Hibernation enhances contractile responses of basilar artery in ground squirrels: The role of Rho-kinase and NO.

Abstract

Hibernation is accompanied by dramatic decrease of blood flow in many organs due to the increase of their vascular resistances. We compared the responses of mesenteric, renal, and cerebral proximal resistance arteries in summer active (SA) and winter hibernating (WH) ground squirrels and studied the signaling pathways of Rho-kinase and NO. Wire myography and Western blotting were used to assess the arterial responses and protein abundances. Basal tone and contractile responses did not differ between SA and WH squirrels in mesenteric and renal arteries, but were greatly increased in basilar arteries of WH compared to SA. Rho-kinase inhibitor abolished the differences in basilar artery basal tone and contractile responses between WH and SA squirrels, while the content of Rho-kinase II protein in the cerebral arteries did not differ between the groups. NO-synthase inhibitor increased basal tone level and basilar artery contractile responses only in SA but not in WH animals, so that the intergroup differences disappeared. The responses of basilar artery to the NO-donor and eNOS protein content did not differ between the two groups, while nNOS protein content was reduced in WH compared to SA. Therefore, the increase of basilar artery basal tone and contractile responses in hibernating animals is due to the increase of procontractile influence of Rho-kinase and the decrease of anticontractile influence of NO. Localization of high resistance in the hibernating brain at the level of proximal resistance arteries may be important for rapid restoration of cerebral blood flow upon arousal from hibernation.