Autonomic innervation of the canine penile artery and vein in relation to neural mechanisms involved in erection.

Neural control of the penile artery and vein of dogs was investigated using isometric tension recording and microelectrode methods. Field stimulation evoked twitch-like contractions of these two vessels and these contractions were blocked by guanethidine. In the artery, twitch-like contractions were more effectively blocked by yohimbine than by prazosin. During high tone of arterial and venous tissues evoked by noradrenaline (NA) in the presence of guanethidine, field stimulation evoked muscle relaxation that was not affected by atropine but was abolished by tetrodotoxin. In parallel to the mechanical responses, field stimulation evoked excitatory junction potentials (EJPs) in both arterial and venous smooth muscle cells. In the case of the artery, an action potential was superimposed on the EJP. The NA-induced contraction was suppressed by vasoactive intestinal polypeptide (VIP), dose-dependently. On the other hand, alpha, beta-methylene-ATP did not affect the muscle relaxation induced by field stimulation. These results indicate that the penile artery and vein of the dog are innervated by adrenergic excitatory nerves and non-adrenergic, non-cholinergic inhibitory nerves. The transmitter possibly involved in the latter is discussed.