Pre-penile arteries are dominant in the regulation of penile vascular resistance in the rat

The amount of blood dow into the penis that will produce an erection is dep endent on the sum of inflow resistance from the feeder arteries, arterioles and the intra-penile vasculature, In the present study, our objective was to determine quantitatively the contribution to inflow resistance of these different components of the rat penile vasculature. Using methods developed previously, we determined the resistance properties of the isolated perfus ed whole penis in situ, both in an intact system and after serial transacti ons of the vessels. These cuts eliminated progressively larger distal segme nts of the vascular bed. Perfusion pressures were recorded at different flo w rates (0.5-3 ml/min/kg body weight) under conditions of maximal dilatatio n and maximal vasoconstriction induced by methoxamine (MXA, 40 mu g/ml). Regardless of the level of vascular tone, the pudendal artery contributes a pproximately 70% of the total resistance of the penile vasculature, In cont rast, the vasculature within the penis (tip, shaft, crus) contributes only about one quarter of the resistance. penile arterial inflow resistance prop erties both at maximal vasodilation and maximal alpha(1)-adrenergic constri ction are dominated by the extra-penile vasculature in the rat. The implica tions of these findings are that alterations in the pudendal-artery leg vas odilation, vasoconstriction, stenosis) would have primary control of arteri al inflow and suggest an important role for pharmacological agents which ca n promote a more generalized vasodilation leg phosphodiesterase inhibitors) in contrast to selective corpus cavernosal agents.