PT - JOURNAL ARTICLE AU - R. D. KRELL AU - P. N. PATIL TI - COMBINATIONS OF <em>ALPHA</em> AND <em>BETA</em> ADRENERGIC BLOCKERS IN ISOLATED GUINEA-PIG ATRIA DP - 1969 Dec 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 262--271 VI - 170 IP - 2 4099 - http://jpet.aspetjournals.org/content/170/2/262.short 4100 - http://jpet.aspetjournals.org/content/170/2/262.full SO - J Pharmacol Exp Ther1969 Dec 01; 170 AB - The ability of alpha blockers to influence the effectiveness of beta blockade was studied in the isolated guinea-pig atrium. Chronotropic effect was used as the test parameter. Cumulative dose- response curves for the relatively specific beta adrenergic agonist, isoproterenol, were determined in control atria, and for isoproterenol in the presence of 1) phentolamine ( 10-6 M), 2) beta antagonists, (±)-propranolol (3 x 10-7 M), (±)-sotalol (10-6 M), (±)-methoxamine (3 x 10-5 M) and (-)-N-isopropyl-p-nitrophenylethanolamine (10-6 M), and 3) in the presence of phentolamine plus each of the above beta antagonists. The influence of phentolamine on beta adrenergic blockade was determined by comparing dose ratios for beta blockers in the presence and absence of phentolamine. In no case was there antagonism between phentolamine and beta blockers; however, there was a slight tendency for the effects to be additive. Similar results were obtained when Dibenamine (10-5 M) was substituted for phentolamine. © 1969 by The Williams &amp; Wilkins Co.