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

Abstract

The amount of blood¯ow into the penis that will produce an erection is dependent on the sum of in¯ow resistance from the feeder arteries, arterioles and the intra-penile vasculature. In the present study, our objective was to determine quantitatively the contribution to in¯ow resistance of these different components of the rat penile vasculature. Using methods developed previously, we determined the resistance properties of the isolated perfused whole penis in situ, both in an intact system and after serial transactions of the vessels. These cuts eliminated progressively larger distal segments of the vascular bed. Perfusion pressures were recorded at different¯ow rates (0.5 ± 3 mlaminakg body weight) under conditions of maximal dilatation and maximal vasoconstriction induced by methoxamine (MXA, 40 mgaml).Regardless of the level of vascular tone, the pudendal artery contributes approximately 70% of the total resistance of the penile vasculature. In contrast, the vasculature within the penis (tip, shaft, crus) contributes only about one quarter of the resistance. Penile arterial in¯ow resistance properties both at maximal vasodilation and maximal a 1 -adrenergic constriction are dominated by the extra-penile vasculature in the rat. The implications of these ®ndings are that alterations in the pudendal-artery (eg vasodilation, vasoconstriction, stenosis) would have primary control of arterial in¯ow and suggest an important role for pharmacological agents which can promote a more generalized vasodilation (eg phosphodiesterase inhibitors) in contrast to selective corpus cavernosal agents.

Role of Adenosine Receptor(s) in the Control of Vascular Tone in the Mouse Pudendal Artery

“…However, this study is the first to characterize the contribution of ARs in the regulation of PA vascular tone, the major artery supplying and controlling blood flow to the penis (Manabe et al, 2000;Hale et al, 2009). In the first set of experiments, we observed that the adenosine analog NECA caused a concentration-dependent vasorelaxation in murine PAs.…”

“…In the PA, the absence of capillaries allows for a rapid filling of cavernosal sinuses during erection (Hale et al, 2009). Recent studies have shown that the PA contributes approximately 70% of total pudendal-penile vascular resistance, whereas the intrapenile vasculature contributes less than 25% of total resistance in this bed (Manabe et al, 2000). In addition, it has been demonstrated that optimal erection requires vasodilation of both prepenile arteries, such as the PA, as well as intrapenile arteries (Manabe et al, 2000;Hale et al, 2009;Hannan et al, 2011).…”

Common Therapeutic Strategies in the Management of Sexual Dysfunction and Cardiovascular Disease

“…Typically, the major locus of resistance in vascular beds lies in the resistance arteries of less than 100µm diameter [32]. We previously addressed this issue in animal studies and discovered approximately 70% of the total pudendal-penile vascular resistance comes from prepenile vessels and not from the small cavernosal and precavernosal intra-penile arterioles [33]. Further, it has been demonstrated that optimal erections require vasodilation of both the pre-penile vessels such as the pudendal, as well as the intra-cavernosal arteries [33].…”

The penis is not protected — in hypertension there are vascular changes in the penis which are similar to those in other vascular beds

“…20 In contrast, if the penis were protected from these structural changes, there would be an increased capacity for blood¯ow to the penis, that is the spontaneously hypertensive rat (SHR) would then be a`potent' model for the study of erectile function.…”