CULTURE OF RAT-BRAIN PREOPTIC AREA NEURONS - EFFECTS OF SEX STEROIDS

The aim of the present study was to investigate the direct effects of testosterone (T), estradiol-17alpha (E2) and 5alpha-dihydrotestosterone (5alpha-DHT) on the survival of neurons and the morphology of neuronal processes (the total process length, the number of processes and the number of process branchings) of the cells derived from neonatal rat preoptic area (POA) to analyze the bases of morphological sexual dimorphism of the POA. The POA cells were exposed to sex steroids during 2-14 days of culture in serum-free medium. Neuronal survival was significantly greater in cultures treated with 1.0 nM T than controls. Although T at any concentration tested (0.1, 1.0 or 10.0 nM) failed to affect the mean value of the process length, a significant difference was observed in the frequency distribution of total process length between 1.0 nM T-treated cultures and control cultures. By 1.0 nM T, the number of process branchings was also significantly increased. In contrast, the number of neurons and the total process length of neurons were not affected by 5alpha-DHT. However, the number of process branchings was significantly increased by 0.1 nM 5alpha-DHT. E2 had no significant effect on any of these parameters. These results suggest that T directly enhances the survival of neurons and increases the dendritic and/or axonic field of the POA, which serves, at least partly, for the development of morphological sexual dimorphism in the rat.