Short-term implantation of oestrogen into the anterior amygdaloid area of immature rats delays the first pubertal ovulation.

Unilateral implants containing oestradiol benzoate (OB) and cholesterol at the ratio of 1 + 4 were placed for 48 h either in the region of the anterior amygdaloid area (AAA) and nucleus of the lateral olfactory tract (NLOT) or in the anterior or posterior part of the mediocortical amygdala of immature 26-day-old female rats, and the age at vaginal opening and the first ovulation was recorded. Whereas implants located in the mediocortical amygdala did not influence the occurrence of ovulation or advanced it distinctively, implantation of OB into the AAA/NLOT resulted in a highly significant delay of the first pubertal ovulation that was associated with postpubertal persistent vaginal cornification in part of the rats.