EFFECTS OF PRENATAL TESTOSTERONE ON SEXUAL-BEHAVIOR, REPRODUCTIVE MORPHOLOGY AND LH-SECRETION IN THE FEMALE RAT

Sexual differentiation of many brain structures and functions is depen dent on levels of testosterone (T) or its metabolites during certain ' sensitive' developmental periods. If T is present during these perinat al periods, masculinization and defeminization of sexual behavior occu r; also, reproductive physiology, and central nervous system morpholog y and function are altered. The purpose of the present study was to ch aracterize the influence of T at specific prenatal developmental inter vals on offspring reproductive morphology? physiology, locomotor activ ity and sexual behavior during postnatal development. To avoid complic ations induced by endogenous testicular activity, only females were ex amined. Free T was used because of its relative short half-life, so th at the effects induced by its administration on a specific gestational day (GD) could be evaluated. Pregnant rats received a single subcutan eous injection of either sesame oil (controls) or 5 mg of T on GD 16, 17, 18, 19, 20, 21, or 22. Female offspring of pregnant rats exposed t o T displayed significant alterations in morphology and behavior. The anogenital distance, measured at ?5 days postbirth, was significantly increased if T was administered on GD 16, 17 or 18. T treatment on GD 16 or each day thereafter through GD 20 significantly delayed the norm al occurrence of vaginal opening (controls at 37.5 days vs. T treatmen t which ranged from 38.5 to 41.4 days). Abnormal vaginal morphology (e nlarged clitoris) was also observed when T was injected during a simil ar prenatal interval (i.e. GD 16 to GD 22). Furthermore, prenatal T tr eatment on GD 18 (and each day thereafter), until GD 22 significantly decreased lordotic behavior compared to control values. However, expos ure to T, on any prenatal GD did not alter the animals' ability to exh ibit an induced luteinizing hormone (LH) surge. These results suggest that the onset for altered reproductive morphology occurs at least as early as GD 16, whereas the onset of sexual behavior sensitivity occur s precisely at GD 18, and that the normal pattern of adult LH release in females is not altered by prenatal androgen treatment using this sp ecific paradigm.