Electrophysiological aspects of the action of bunaphtide on single cardiac muscle fibres

The action of Bunaphtide N (2-diethylamine-ethyl) N(n-butyl)-α-Naphtamide, a new antiarrhythmic compound, has been studied on single cardiac muscle fibres. Electrophysiological aspects have been considered, comparing action potentials recorded from single cardiac fibres perfused in Tyrode and Tyrode+Bunaphtide (24 γ/1 - 1000 γ/1). Experiments have been carried out on atrial cells, Purkinje fibres and papillary muscles. Idioventricular rhythm has been obtained from papillary muscles preparations where ectopic centre has been brought into action. In the atrial zones drug reduces the duration of the action potential within the first 30 sec of contact; after 10 min of perfusion, however Bunaphtide caused a significant lengthening. Rate was reduced by 20-25%. An increase (18%) in amplitude of the potential (hyperpolarisation) has been observed. In cells contiguous to the sino-atrial pacemaker (not real pacemaker zones) and in ectopic centre, effect of Bunaphtide consisted of reducing the level of the potential, damping the slow subliminal oscillations of membrane resting potentials.