Pharmacophysiological Change of Rabbit Corpus Cavernosum under Hypoxia

Park, Heung Jae; Kim, Je Jong; Koh, Sung Kun

Abstract

Local contributing factors in penile erection are trabecular smooth muscle, endothelium, trabecular fibroelastic components, tunica albuginea and local neuro-control. There are three neuroeffector systems in local neuro-control for penile erection. One is adrenergic system causing contraction and the others are cholinergic and noncholinergic nonadrenergic system causing relaxation of corpus cavernosum under normoxia. The effect of these systems under hypoxic condition however is not fully understood. The aims of this study were to detect the pharmacophysiological changes of corporal smooth muscle about 3 local neuroeffector systems under hypoxia in the rabbit and to apply the results of study to the management of the priapism. The strips of rabbit corporal tissues were studied for isometric tension measurement under normoxia, hypoxia and cooling condition in the organ chambers. Influence of NL- monomethyl-L-arginine (L-NMMA) and L-arginine to acetylcholine under normoxia and effects of phenylephrine, norepinephrine, acetylcholine, VIP, endothelin 1, papaverine and KCI on the rabbit corpus cavernosal tissue were monitored under normoxia and hypoxia and changes under cooling condition were observed. Relaxing effect of acetylcholine under normoxia was suppressed with L-NMMA and this suppression was reversed with L-arginine. Relaxation with acetylcholine and contraction with endothelin 1 were suppressed under hypoxic condition. Contracting effect of norepinephrine and phenylephrine was stronger under hypoxia or cooling condition than normoxia or 37 degrees C condition respectively. Relaxing effect of VIP and papaverine on corpus cavernosa was similar under normoxia or hypoxia. These results suggest that endothelium-dependent relaxation by cholinergic and noncholinergic nonadrenergic system and endothelium-dependent contraction by endothelin 1 are suppressed under hypoxic condition. VIP related noncholinergic nonadrenergic relaxation and direct relaxation effect of papaverine to corporal smooth muscle are preserved under hypoxia. Application of adrenergics and local irrigation with cold saline would be effective in the management of priapism.