Neonatal gonadal hormone treatments and adult open-field behavior in female rats.

The present study was conducted to investigate the effect of neonatal gonadal hormone treatments on the rat's emotionality in adult life. Female Sprague-Dawley rats treated subcutaneously on the day of birth with 100 micrograms of 17 beta-estradiol (E) or 1000 micrograms of testosterone propionate [TP] or 1000 micrograms of dihydrotestosterone[DHT] were tested in the open-field apparatus on 5 consecutive days at 6 months of age. All TP-treated rats and 6 out of 11 E-treated rats exhibited the persistent estrus on the vaginal smears, while DHT-treated rats and control rats did not show such changes in estrus cycle. Highly significant difference in either ambulation and defecation scores was found between persistent estrus and normal estrus cycle rats in E-treated group: persistent estrus rats showed higher ambulation and lower defecation than normal estrus cycle rats. As compared with the control level TP-treated persistent estrus rats showed a lower defecation score. These findings indicate that persistent estrus rats induced by E or TP are in the state of low emotionality. A possible relationship between the emotionality and the induction of mammary carcinomas was discussed.