Age-related effects on genital reflexes induced by paradoxical sleep deprivation and cocaine in rats.

Although sexual function often decreases with age, a recent study demonstrated that paradoxical sleep deprivation (PSD) was effective in inducing penile erection (PE) in 60% of 22-month-old PSD rats after acute cocaine injection, whereas this behavior was absent in non-PSD control rats. The present study sought to compare alterations in genital reflexes (PE and ejaculation-EJ) induced by PSD followed by acute cocaine or saline at different points in the life span of male rats. Rats of different ages (3, 6, 10, 12, 18, 22 and 28 months), were given a single injection of either saline or cocaine (7 mg/kg, i.p.) after a 4-day period of PSD, and then evaluated for genital reflexes. Results indicated that genital reflexes in PSD rats given saline become less frequent with age and disappear after the age of 18 months. However, cocaine potentiated and prolonged these behaviors until the age of 22 months. Although a number of factors are involved in such a complex phenomenon as PE, we suggest that the previously documented dopamine receptor supersensitivity induced by PSD may be an important contributor to the potentiation by cocaine of genital reflexes after sleep deprivation.