PRENATAL INHIBITION OF AROMATASE-ACTIVITY AFFECTS LUTEINIZING-HORMONEFEEDBACK MECHANISMS AND REPRODUCTIVE BEHAVIORS OF ADULT GUINEA-PIGS

The necessity of brain aromatization for sexual differentiation was in vestigated by treating pregnant guinea pigs with an aromatase inhibito r, 1,4,6-androstatriene-3,17-dione (ATD), from Day 30 to Day 55 of ges tation. In postnatal Week 16, subjects were gonadectomized, and blood samples were collected after treatment with 10 mu g estradiol benzoate (EB), used to elicit an LH surge; subjects were subsequently treated with GnRH to test pituitary responsiveness. Plasma samples were assaye d for LH by RIA. Prenatal ATD treatment did not affect the organizatio n of the LH surge mechanism in either male or female subjects. AU anim als, regardless of sex or treatment, released LH after GnRH treatment, but the responsiveness of the gonadotroph to GnRH was attenuated in b oth males and females treated with ATD in utero. In addition, a signif icant sex difference in the pattern of LH released in response to a Gn RH challenge was found. ATD-treated animals did not respond to the neg ative feedback actions of EB on LW secretion (p < 0.05), and the perce ntage of males displaying lordosis behavior was greater in this group than in controls (p < 0.05). Mounting behavior and lordosis behavior o f females were not significantly affected by treatment. These data dem onstrate a need for estrogen in the organization of brain areas that m ediate negative feedback control of LH in both sexes and lordosis beha vior in the male guinea pig. The organization of positive feedback mec hanisms for controlling LH seems to be under androgenic control. Our d ata also suggest that the responsiveness of the gonadotroph to GnRH ac tion is developmentally coordinated by prenatal estrogen and is sexual ly differentiated.