title: Effect of ethanol on guinea pig ventricular action potentials.
abstract: The effects of low concentrations of ethanol on transmembrane potentials of guinea pig ventricular muscle were analyzed. Papillary muscles were superfused with Tyrode solution in vitro at 30 degree C while driven at 60 min-1. Transmembrane potentials were recorded by means of intracellular microelectrodes before, during and after a 15 min exposure to ethanol. Ethanol 2,5 mg/100 ml (0.55mM) did not affect transmembrane potentials. Ethanol 5 mg/100 ml enhanced the amplitude of the action potential (AAP) without affecting the membrane resting potential (MRP) and the maximum velocity of the upstroke (dV/dt). Ethanol 40 mg/100 ml also enhanced AAP without modifying MRP and dV/dt. Verapamil and propranolol blocked the augmenting effect of ethanol on AAP. Ethanol 40 mg/100 ml also enhanced the amplitude of responses restored by norepinephrine in fibers depolarized by high [K]0 to a level of resting potential at which the fast component of the upstroke was abolished. The enhancement of AAP was accompanied by a shift of the plateau to more positive values, but the duration of the action potential measured at 50% of repolarization was not affected. The results indicate that ethanol in low concentrations augments, through a catechol-mediated effect, the slow component of the upstroke of ventricular action potentials.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002396:Catechols / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology
chemical_list: D002396:Catechols; D000431:Ethanol; D011433:Propranolol; D009638:Norepinephrine