Sex Difference in the Effects of Electrochemical Stimulative Lesions of the Limbic-Preoptic Area on the Onset of Puberty in the Rat

Electrochemical stimulative lesions were produced in various brain areas of 28-day-old male and female rats, and the effects on puberty were examined, employing as the criteria of puberty the appearance of sperm in the testes for the male and vaginal opening and first ovulation for the female. In the male rat, the stimulative lesion produced either in the hippocampus, the lateral part of the amygdala, or the medial preoptic area significantly delayed puberty. In the female, the stimulative lesions produced in the hippocampus or the lateral part of the amygdala advanced the time of the vaginal opening and the first ovulation, whereas the stimulative lesions produced in the medial preoptic area had no effect on puberty. It was suggested that a sex difference exists in the function of the hippocampus and the lateral amygdala in the control of gonadotropin release in immature rats.