Hormonal mechanisms underlying aberrant sexual differentiation in male rats prenatally exposed to alcohol, stress, or both.

Abstract

The male offspring of rats exposed to restraint stress, alcohol, or both during late pregnancy show normally masculinized genitalia; however, sexual differentiation of behavior is dissociated from the external morphology. In contrast to controls, males exposed prenatally to stress, alcohol, or a combination of these factors exhibited the female lordotic pattern. Thus, all 3 prenatal treatments led to incomplete behavioral defeminization. Behavioral masculinization was not altered by fetal alcohol exposure alone, but a significant number of males that experienced prenatal stress alone failed to copulate. A more severe disruption of behavioral masculinization occurred when stress and alcohol were combined. Very few males exposed to the combination treatment mated with females. This study attempted to relate the effects of these treatments on sexual behavior to the postparturitional surge in plasma testosterone (T) that is known to influence the process of sexual differentiation. Prenatally stressed males, like control males showed a large, brief surge in plasma T that peaked 1 hr after delivery. Altered defeminization and masculinization were seen in prenatally stressed males, despite a normal postparturitional T surge. Fetal alcohol exposure, with or without concomitant stress, depressed T to the same extent right after birth and led to a similarly blunted T surge 1 hr later. Thus, equal disruption of the neonatal T pattern occurred in alcohol-alone males, who showed normal male copulatory behavior, and in alcohol-plus-stress males, whose behavior was severely attenuated. The results suggest that consideration of abnormal exposure to T during prenatal ontogeny may be required to understand the atypical sexual behaviors associated with these treatments.