Physiological aging and penile erectile function: a study in the rat.

Erectile function of adult (8-month-old) and aged (27-month-old) rats was investigated by in vivo and in vitro assays. Reflexogenic tonic erections were evoked in vivo by electrostimulation of the dorsal nerve of the penis. Aged rats developed tendentially low intracavernosal pressures, and the kinetics of erection and detumescence were significantly lower than in adult animals. The erectile tissue isolated from aged rats exhibited poor response to papaverine. When precontracted with norepinephrine, aged tissues required a 3-fold increase of papaverine concentration to full relaxation. Functional measurements were coupled with morphological analysis of elastic fibres of the tunica albuginea. Light microscopy showed degenerative signs of elastic fibres of aged rat specimens. Taken together, the present findings show that physiological aging is associated with penile tissue stiffness and abnormal corporal compliance.