Action potentials in rat muscle with twitch tension potentiated by KCI treatment, adrenalectomy, tetanus and treppe.

I N A previous study (I) it was found that the response of rat muscle to single stimuli showed a greater developed tension and a longer contraction time in adrenalectomized animals than in normal controls. The increased contraction time and the prolonged action potentials observed after adrenalectomy led to the suggestion that repetition might account for a part of the increased tension. In the same report it was shown that the response of muscle potentiated by intraperitoneal injection of KC1 had a longer contraction time than the response of untreated muscle. Brown (2) studied the effect of K on the action potential in muscle of the cat after intra-arterial injection of KCl. This investigator observed a decrease in height of the action potential but he did not report a change in duration of the action potential or an increase of contraction time of the KCl-treated muscle. In a recent report (3) it was shown that the increased tension in responses of muscle to single stimuli in rats treated with desoxycorticosterone acetate is accompanied by repetitive action potentials. differ from those seen after KC1 treatment, adrknalectomy disappear after the third to sixth response to single stimuli. However, these potentiated responses and tetanus in that they