Effects of alpha-2 blockade on sexual response: experimental studies with delequamine (RS15385)

The role of alpha-2 receptors and alpha-2 antagonists in central and peripheral mechanisms of sexual response are discussed. It is concluded that the predominant role of the alpha-2 antagonist centrally is to increase arousal which in certain circumstances, is sexual. It is further concluded that the predominant role of the alpha-2 antagonist peripherally is to modulate (block) the norepinephrine (NE)-induced contractility in the smooth muscle of the penis. How the central arousal mechanisms are specifically linked to sexual response is not understood. Experimental studies with a selective alpha-2 antagonist, delequamine, are briefly reviewed and their complex results discussed. Evidence from sleep studies was consistent with delequamine having both central excitatory and inhibitory effects, dependent on dosage. The possibility that men with psychogenic erectile dysfunction might have increased central alpha-2 tone was considered. The apparent loss of responsiveness to the alpha-2 antagonist in older dysfunctional men was discussed. More questions are raised than answered; further research is needed in this area.