Pharmacology of the erectile tissue of the canine penis.

To assess the role of different neuroeffector systems in penile erection, pharmacological agents were tested in vitro using strips of corpus cavernosum tissue from the dog. Alpha-adrenoceptor agonists, K+ or histamine caused concentration-dependent contraction. Tyramine caused a poorly sustained contraction, as did nicotine in some cases. In precontracted preparations, relaxation was caused by beta2-adrenoceptor or muscarinic cholinoceptor agonists, or by vasoactive intestinal peptide. The results suggest that a noradrenergic alpha-adrenoceptor system maintains penile flaccidity in the dog. Penile erection may result from the activation of inhibitory beta2-adrenergic, muscarinic and/or peptidergic systems.