RESTORATION OF SEXUAL-BEHAVIOR IN AGED MALE-RATS BY INTRACEREBRAL GRAFTS OF FETAL PREOPTIC AREA NEURONS

A decline in sexual arousal and copulatory activity has been observed in male rats with advancing age. Grafting of fetal hypothalamic tissue into the third ventricle of aged male rats restores sexual behavior. This study investigated the effects of grafting fetal preoptic area (P OA) neurons into the POA of aged male rats exhibiting decreased sexual behavior. We grafted suspensions of fetal POA neurons into the POA of 20 aged (19 to 24 months old) male rats that displayed no ejaculation . From 2 weeks after grafting, one or more series of male copulatory a ctivity and sexual motivation tests were performed at intervals of 3 t o 4 weeks. Three behavioral tests given 5 days apart were repeated for each animal in each series. Among the 20 aged rates with the fetal gr afts, 15 showed improved sexual motivation, and 14 of these had copula tory activity restored to levels comparable with those of young males. Among these 14 rats, eight ejaculated during copulation. Copulatory b ehavior was restored between 21 and 45 days after grafting and persist ed until the end of observation (2-4.5 months). Sexual performance did not improve in control aged male rats grafted with either fetal cereb ral cortex neurons into the POA and POA neurons into the ventromedial hypothalamus. The rats that received grafts of fetal POA neurons into the POA and recovered sexual performance also showed improvement or re covery to levels comparable to those in young males of serum testoster one concentrations, serum luteinizing hormone levels after castration, and the post-castration rise in luteinizing hormone. These results in dicate that decreases in copulatory activity, sexual motivation, and s ome neuroendocrine functions in aged male rats are at least partially due to dysfunction of the POA.