Calcium antagonists: systemic and regional haemodynamic effects in conscious spontaneously hypertensive rats (SHR).
The systemic and regional (renal, mesenteric and hindquarter) haemodynamic effects of the calcium antagonists verapamil, nifedipine and PY 108-068 [diethyl 4-(2, 1, 3-benzoxadiazol-4-yl)-1, 4-dihydro-2, 6-dimethylpyridine-3, 5-dicarboxylate] were studied in conscious, chronically instrumented spontaneously hypertensive rats (SHR). All three calcium antagonists caused a dose-dependent fall in mean arterial pressure (MAP) and total peripheral resistance. In intact animals the fall in resistance was related primarily to a vasodilatation in the hindquarter (mainly muscular) vascular bed. During the early fall in blood pressure a reflex rise in cardiac output and heart rate was observed following nifedipine and PY 108-068, but not after verapamil. Following sinoaortic baroreflex denervation the dose-response curve for the calcium antagonist-induced fall in blood pressure and total peripheral resistance was shifted to the left. Moreover, the calcium antagonists then caused a comparable degree of vasodilation in all three vascular beds studied. It is concluded that calcium antagonists preferentially dilate the muscular bed in intact animals; however, sinoaortic baroreflex denervation unmasks an unselective pattern of vasodilatation.
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D012018:Reflex / Q000187:drug effects; D012849:Sinoatrial Node / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology; D014851:Wakefulness / Q000187:drug effects*
D002121:Calcium Channel Blockers; D014700:Verapamil; D009543:Nifedipine; C034600:darodipine