Relationship between sexual behavior and sexually dimorphic structures in the anterior hypothalamus in control and prenatally stressed male rats

The present study was designed to examine the effects of prenatal stress on the morphological development of sexually dimorphic structures in the anterior hypothalamus in male rats and to determine if there is a relationship between morphologic development of the brain and copulatory behavior in individual animals. Dams in the stress group were subjected to treatments of heat-light restraint during the third trimester of gestation (day 14 to parturition) three times daily for 45-min periods. At 90 days of age, prenatally stressed and control male offspring were tested during the dark cycle for spontaneous male sexual behavior. Volumes of the sexually dimorphic nucleus of the preoptic area (SDN-POA) and the anteroventral periventricular nucleus (AVPV) were measured. Comparisons were made between copulatory behavior and hypothalamic nuclear volumes. SDN-POA volumes were significantly reduced (feminized; males have a larger SDN-POA than females) in prenatally stressed males that did not copulate, whereas, SDN-POA volumes in prenatally stressed males that copulated were not altered. The few control males that did not copulate (sexually non-active) also had significantly reduced SDN-POA volumes compared to the control males that did copulate (sexually active). The volume of the AVPV was significantly increased (feminized; males have a smaller AVPV than females) in prenatally stressed males that were sexually non-active compared to AVPV volumes in sexually active males. The results obtained in this study provide a strong positive relationship between sexual behavior and the morphology of the two sexually dimorphic structures measured.