Original Article

Effect of scopolamine on action potential of myocardial cell of guinea pig

Zhen-yuan LI


Action potential of myocardial cell of isolated ventricular septum was recorded by intracellular capillary glass electrode. The duration of action potential (APD) was prolonged from 91±31 ms and 142±39 ms to 115±35 ms and 179±50 ms for APD50 and APD100, respectively by scopolamine 50 μg/ml (p<0.001). The postrepolarization refractory period (PRP) was prolonged greatly from 154±40 ms to 222±80 ms, and the ratio of PRP to APD was increased from 1.6±0.4 to 2.2±0.5 for APD50 30 min after scopolamine. The spontaneous actibity of cardiac cell was decreased from 146±32 beats/min to 92±42 beats/min(30 min). The effects of scopolamine on APD did not show up when theβ-receptors had been blocked by propranolol and the α-receptors had been activated by methoxamine. Scopolamine is supposed to block the reentry excitation by increasing the pacemaker by decreasing the spontaneous activity.

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