TY - JOUR T1 - INDUCTION OF AUTOMATICITY IN CAT PAPILLARY MUSCLES BY SYMPATHOMIMETIC AMINES JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 70 LP - 75 VL - 133 IS - 1 AU - Peter E. Dresel AU - Diana G. Duncan Y1 - 1961/07/01 UR - http://jpet.aspetjournals.org/content/133/1/70.abstract N2 - It has been possible to study quantitatively the induction of automaticity in isolated quiescent or electrically-driven cat papillary muscle preparation. Epinephrine and norepinephrine were found to be equipotent, while isoproterenol was 7 times more potent than the above. Methoxamine had no effect. The threshold for induction of automaticity by epinephrine is increased by raising the potassium concentration of the bath fluid or by prior treatment with dichloroisoproterenol. Small concentrations of chloroform in the medium cause a slight decrease in threshold in most muscles. Phenoxybenzamine has the same effect. ER -