In the present study we investigated the in vitro relaxant response of erectile tissue obtained from rabbits of different ages (3, 7 and 24 months) in order to detect the progression with age of cavernosal activity in response to substances acting via endothelium-dependent or -independent mechanisms. Noradrenaline induced a concentration-dependent contraction (0.1 ~M-3 mM), with an increase in the contractility in the 24-month-old group. Ace@choline produced a concentration-dependent relaxant effect in the three age groups, with a reduction of the maximal relaxant effect in older animals. ATP (10 ~tM-1 raM) and adenosine (10 gM-1 mM) induced a concentration-dependent relaxant effect that was higher in the older group. The presence of the NO-synthase inhibitor NO'-nitro-L-arginine methyl ester (L-NAME) (0.1 raM) or of the P2purinoceptor antagonist suramin did not affect ATP relaxation. Relaxation induced by sodium nitrite and nifedipine was reduced in older animals. In conclusion, aging selectively alters the in vitro responsiveness of rabbit erectile tissue. Purinergic system remains more active despite a decrease in the maximal endothelial cholinergic activity and the direct smooth muscle relaxant component.