title: Antagonism of the effect of isoprenaline on heart rate by pilocarpine.
abstract: 1 The interaction of pilocarpine and isoprenaline on heart rate was investigated in the spontaneously beating, right isolated atrium of the rat.2 The log dose-effect curve of isoprenaline, measured in the presence of various concentrations of pilocarpine, was not modified when the concentration of the latter did not exceed 10(-6)M even though significant slowing of the heart had occurred. At concentrations higher than 10(-6)M a rapid but graded shift to the right of isoprenaline response curves occurred so that at pilocarpine 10(-5)M the pD(2) of isoprenaline was reduced from 11 to 3.3; cocaine slightly reduced this antagonism.3 It is concluded that pilocarpine antagonizes isoprenaline by some mechanism which is not of the simple competitive type.
mesh_terms: D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D005260:Female; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008297:Male; D010862:Pilocarpine / Q000494:pharmacology*; D051381:Rats; D013268:Stimulation, Chemical
chemical_list: D010862:Pilocarpine; D003042:Cocaine; D007545:Isoproterenol