title: Effects of betacarbolines on the automaticity of the guinea pig sinus node.
abstract: The effects of betacarbolines on guinea-pig isolated sinus nodes superfused with Tyrode's solution at 35 degrees C were analyzed. All analogs depressed the automaticity. The phase 4 of transitional fibers was depressed, in the absence of any change in maximum diastolic potential. The threshold for harmaline action was 10(-7)M. Dehydrogeneration of harmaline into harmine increased the potency. Removal of the methoxy group (harmane) did not modify the potency but accelerated the recovery. Substitution of the methoxy group by a hydroxy group (harmalol and harmol) reduced markedly the potency of harmaline and harmine, respectively.
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006246:Harmaline / Q000494:pharmacology*; D006247:Harmine / Q000031:analogs & derivatives / Q000494:pharmacology*; D012849:Sinoatrial Node / Q000187:drug effects*; D013329:Structure-Activity Relationship
chemical_list: D000470:Alkaloids; C001326:harmol; D006247:Harmine; C005010:harman; D006246:Harmaline