Effects of some calcium channel blockers on isolated human penile erectile tissues

The effects of the calcium channel blockers (CCBs) verapamil, nifedipine and diltiazem on contractile activation of isolated human penile erectile tissues were investigated. Specimens of the corpus spongiosum (CS) and corpora cavernosa (CC) were obtained from men with a history of normal penile erection undergoing cystourethrectomy because of bladder malignancy. Preparations were mounted in organ baths and isometric tension was recorded. Deprivation of extracellular calcium abolished electrically induced contractions in both CS and CC preparations within 15 min.; norepinephrine (NE)-induced contractions were reduced by 90% (CS) and 83% (CC) after 30 min. All the CCBs reduced electrically induced contractions concentration-dependently, nifedipine being the most potent agent. Contractions induced by exogenous NE were depressed by about 50%, whereas high K+ (124 mM) induced responses were abolished. It is concluded that contraction in penile erectile tissues is mediated mainly by neuronally released NE stimulating postjunctional alpha-adrenoceptors. The contraction is highly dependent on extracellular calcium and can partly be inhibited by CCBs. It cannot be excluded that some CCBs injected intracavernosally may be useful for diagnosis and even treatment of erectile dysfunction. However, calcium channel blockade may not be as effective as a therapeutic principle as blockade of alpha-adrenoceptors.