Dissociation of the restoration of copulatory behavior and the testicular morphology in old male rats with fetal brain grafting.

Improvement of copulatory activity has been reported in aged male rats bearing the fetal preoptic area (POA), however, whether the fetal POA graft has any effect on the gonad of aged male rats has not been established. In the present study, the testicular histology and the sexual behavior were studied in 20 old (18-19 months) Long-Evans male rats after fetal brain transplantation. Animals were divided into three groups: (1) POA-grafted group (n = 6): fetal POA neurons were grafted into the POA, (2) COR-grafted group (n = 7): fetal cerebral cortex tissue was grafted into the POA and (3) SHAM-grafted group (n = 7): the POA of rats received glucose-saline injection. Thirty days after the grafting, only those bearing POA graft showed an increase in mount frequency and intromission frequency. Sixty days after fetal brain grafting, testicular morphology was examined. Testicular volume was measured and paraffin sections (8 microns) of the testis were stained with Hematoxylin-Eosin. Seminiferous tubular diameter and epithelial height were analyzed quantitatively. No significant changes in testicular volume, seminiferous tubular diameter and epithelial height were observed in all three groups. The shrunk testicular morphology in the aged male rats cannot be restored by fetal POA grafting. These results suggest that copulatory behavior and testicular morphology may be dissociated in old male rats.