Histamine-induced early afterdepolarizations and triggered activity in guinea-pig papillary muscles
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The effects of histamine on the transmembrane action potentials were studied with computerized standard microelectrode technique in guinea-pig papillary muscles. Experiments offered evidence that histamine (6.0mol / L) caused a significant diminution in action potential duration at 50% repolarization (APD50) and 90% repolarization (APD90) (data from no abnormal automaticity and oscillatory potential cells). Histamine could induce early afterdepolarizations (BAD, 57%), oscillatory potentials and triggered activity. HAD frequently occurred at low stimulation frequencies (0.2- 1.0Hz) with prolongation of the action potential duration. EAD-in-duced triggered activity exhibited fast spontaneous action potential (14%). The results suggested that histamine-induced EAD and triggered activity might relate to the autorhythmic tachyarrhythmias seen in cardiac anaphylaxis, etc.