title: Profile of a new prazosin congener, BL-5111A. Studies in the rat.
abstract: 1. The effects on blood pressure and heart rate of prazosin and a structurally-related congener, BL-5111A, were compared in conscious and anaesthetized rats. 2. Both agents induced dose-related falls in systolic and diastolic blood pressure, with relatively little effect on heart rate. The hypotensive potency of prazosin was twenty-fold greater than that of BL-5111A. 3. The hypotensive activity of prazosin was abolished by pretreatment with the ganglionic blocking agent, pentolinium, or the alpha-adenoceptor blocking agent, phentolamine, whereas BL-5111A retained significant hypotensive activity (up to 28%) after either pretreatment. 4. Both prazosin and BL-5111A attenuated pressor responses to noradrenaline, and reversed the responses to adrenaline, prazosin being, in this respect, 6 times more potent than BL-5111A. There was a highly significant relationship between the alpha-adrenoceptor blocking activity of either agents and its hypotensive effect. 5. BL-5111A differed from prazosin in possessing, in addition to its predominant alpha-adrenoceptor blocking action, a minor component of action attributable to direct vasodilatation.
mesh_terms: D000758:Anesthesia; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004837:Epinephrine / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology*; D051381:Rats; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D011799:Quinazolines; D014665:Vasodilator Agents; D000804:Angiotensin II; C019578:tiodazosin; D011224:Prazosin; D004837:Epinephrine