TY - JOUR T1 - THE INFLUENCE OF DRUGS ON THE IRRITABILITY AND AUTOMATICITY OF HEART MUSCLE JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 215 LP - 223 VL - 98 IS - 3 AU - THEODORE H. GREINER AU - SOLOMON GARB Y1 - 1950/03/01 UR - http://jpet.aspetjournals.org/content/98/3/215.abstract N2 - 1. The effects of seven ions and sixteen drugs on the irritability and automaticity of heart muscle are reported. 2. The cations studied, other than barium, all raised the threshold of irritability. The curves for lithium and sodium were similar. Potassium and ammonium raised the threshold of irritability sharply, beyond a certain concentration. Calcium and magnesium produced a slight rise in threshold. The response to barium was erratic. 3. The sympathomimetic amines all lowered the threshold of irritability and all produced spontaneous rhythms. The N-isopropyl homologue of epinephrine was most effective in lowering the threshold, but produced less automaticity than the other homologues. 4. Papaverine and aminophylline lowered the threshold of irritability, while quinidine and procaine elevated it, in concentrations which are attainable in an intact animal. 5. Atropine, acetylcholine, and acetyl-β-methylcholine had no demonstrable effect on irritability or automaticity. 6. The difference between irritability and automaticity of myocardium is illustrated by the changes induced by drugs. 1950 by The American Society for Pharmacology and Experimental Therapeutics ER -