EFFECTS OF RESERPINE ON ELECTRICAL RESPONSES EVOKED BY PERIVASCULAR NERVE STIMULATION IN THE RABBIT EAR ARTERY

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Abstract
In the rabbit ear artery, stimulation ofperivascular nerves elicited an excitatory junction potential (e.j.p.) and a slow depolarization; the amplitude of the e.j.p. related to that of the slow depolarization. In the artery from the reserpine-treated rabbit, the slow depolarization was abolished, and only the e.j.p. was generated, even with intensive stimulation. Reserpine treatment reduced the tissue content of noradrenaline below 1% of the control, and abolished the outflow of noradrenaline induced by perivascular nerve stimulation; depolarization of smooth muscle membrane to exogenously applied noradrenaline remained unchanged under this condition. Thus, the reserpine treatment dissociated the e.j.p. from the slow depolarization, and the latter component related to the noradrenaline stored in the nerve terminals. Iontophoretic application of noradrenaline or ATP depolarized the smooth muscle membrane of the rabbit ear artery; the former decayed slowly and the latter rapidly. Possible transmitter substances involved in the generation of e.j.p. were discussed.