Analysis of hypotensive mechanisms of pindolol, a beta-adrenoceptor blocking drugs in rats.
The hypotensive mechanisms of pindolol in anesthetized and conscious rats were investigated. Pindolol caused a fall in blood pressure in anesthetized, conscious and spinal rats, though in conscious rats a higher dose of the drug was required to produce such a response. This hypotension with pindolol in anesthetized and conscious rats was markedly inhibited by pretreatment with the drug itself or other beta-adrenoceptor blocking drugs. A similar phenomenon also occurred when isoproterenol was injected intravenously in anesthetized and conscious rats. The relationship between the hypotensive actions of four beta-adrenoceptor blocking drugs in anesthetized rats and their intrinsic beta-sympathomimetic actions in isolated catecholamine-depleted tracheal preparations was determined. Order of hypotensive potencies was the same as that of their intrinsic beta-sympathomimetic action, namely, pindolol greater than carteolol greater than bufetolol in equilibrium propranolol (p less than 0.05). These results suggest that the hypotension with pindolol is mediated through a decrease in the peripheral vascular resistance due to an intrinsic beta-sympathomimetic action of the drug.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000771:Anesthesia, Intravenous; D000818:Animals; D000959:Antihypertensive Agents; D001794:Blood Pressure / Q000187:drug effects; D003243:Consciousness; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007796:Laminectomy; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D010869:Pindolol / Q000494:pharmacology*; D051381:Rats; D013566:Sympathomimetics / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D000959:Antihypertensive Agents; D013566:Sympathomimetics; D010869:Pindolol; D007545:Isoproterenol