An electrophysiological study of excitatory neuromuscular transmission in the guinea-pig main pulmonary artery.

Electrical responses of single smooth muscle cells to perivascular nerve stimulation were recorded in the guinea-pig main pulmonary artery with a micro-electrode, to investigate neuromuscular transmission mechanisms. Perivascular nerve stimulation produced excitatory junction potentials in the smooth muscle cells of the main pulmonary artery. When stimulation was repetitive and of high frequency, a spike was seen in the early part of these potentials. Phentolamine, prazosin, phenoxybenzamine, guanethidine or tetrodotoxin all suppressed first the spike and then the junction potential. Exogenously applied noradrenaline also produced depolarization, and in high concentrations above 10(-6) M, spikes. Phentolamine again suppressed the spikes and then the depolarization. The results suggest that endogenous and exogenous noradrenaline act on the same type of receptor in this artery.