and lactational exposure of male rats to 2,3,7,8-tetrachlorodibenzo--dioxin: Effects on sexual behavior and the regulation of luteinizing hormone secretion in adulthood

Effects of inutero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on sexual differentiation of the central nervous system (CNS) were investigated by examining sexual behavior and luteinizing hormone (LH) secretion in adulthood. The sexual behavior of male rats born to dams given TCDD (0–1.0 μg/kg) on Day 15 of gestation was demasculinized: dose-related increases in mount, intromission, and ejaculation latencies and decreases in copulatory rates were observed. Sexual behavior was also feminized: following castration, estradiol benzoate (EB) priming, and progesterone treatment, males displayed dose-related increases in lordosis frequency and lordosis intensity when mounted by another male. The regulation of LH secretion was feminized as well; progesterone treatment increased plasma LH concentrations in gonadectomized, EB-primed females and TCDD-exposed males but not in control males. These results, which were generally seen in response to a single maternal dose of TCDD as low as 0.16 μg/kg, demonstrate that inutero and lactational TCDD exposure impairs sexual differentiation of the CNS.