Role of cerebral ATP-sensitive K+ channels in arterial pressure regulation during acute cerebral ischaemia in SHR and WKY rats.

1. ATP-sensitive K+ channels (KATP) are activated either by decreased intracellular ATP content or ATP/ADP ratio during ischaemia. We examined the role of a cerebral KATP in arterial pressure regulation during acute cerebral ischaemia using SHR and WKY rats. Thirteen week old male SHR or WKY rats were anaesthetized with urethane, and arterial pressure and heart rate were recorded under an artificial ventilation. 2. Intracerebroventricular (i.c.v.) injections of glibenclamide, a specific inhibitor of KATP, elicited dose-dependent vasopressor responses in WKY with bilateral ligation of carotid arteries, whereas it caused smaller vasopressor responses in SHR than WKY. 3. Systemic administration of AVP V1 receptor antagonist, OPC-21268, abolished the vasopressor responses of i.c.v. injections of glibenclamide in WKY but not in SHR. 4. Intracerebroventricular injections of glibenclamide caused both the increase in plasma concentration of AVP and the decrease in pituitary AVP content in WKY with bilateral ligation of carotid arteries, whereas it elicited no significant change in plasma and pituitary concentration of AVP in SHR with bilateral ligation of carotid arteries. 5. Cerebral KATP may play a role in the protection of excess hypertension by inhibiting AVP release from the pituitary glands during acute ischaemia in WKY, but this mechanism might not work in SHR during acute cerebral ischaemia.