Reduced sensitivity of penile mechanoreceptors in aging rats with sexual dysfunction.

Male sexual activity gradually declines with age in most mammalian species and may be associated with a decrease in vibrotactile sensitivity of the penis. This study was designed to determine if the penile mechanoreceptors in aging rats exhibit reduced sensitivity to vibrotactile stimuli. Electrophysiological and behavioral data was obtained from mature adult (9 months) and old (23 months) rats. Single penile mechanoreceptor afferent fibers from aging animals exhibited a decrease in the ability to transduce high-frequency vibratory stimuli when compared to afferents from mature adult animals. In addition, there was a reduction in single-fiber and sensory nerve conduction velocity. Copulatory performance was reduced in the aging animals as determined by the inability to ejaculate with a receptive female. The results of this study demonstrate that the male rat exhibits an age-related decrease in penile vibrotactile sensitivity mediated by mechanoreceptor afferents which may be partly responsible for the decrease in parameters of sexual activity.