Two components in the cellular response of rat tail arteries to nerve stimulation.

1. The response of rat tail arteries to stimulation of perivascular nerves was studied with intracellular micro-electrodes. 2. E.j.p.s were recorded from all smooth muscle cells. With higher stimulus strength, a slow depolarization that lasted for more than 30 sec also appeared. Repetitive stimulation was more effective in eliciting this slow component than were single pulses. 3. E.j.p.s were resistant to phentolamine and yohimbine. However, guanethidine and sympathetic denervation with reserpine and 6-hydroxydopamine depressed e.j.p.s. 4. The slow depolarization was readily blocked by phentolamine (1 x 10(-6) g/ml.) and potentiated by cocaine (1 x 10(-6) g/ml.). 5. It is proposed that vascular smooth muscle activity can be regulated neurally by both the e.j.p. and the slow depolarization.