Abstract
Immature individuals under the development are considered to have high sensitivity and vulnerability to chemical exposure. The brain is sexually differentiated under the influence of testosterone secreted from the testes during developing period. Inhalation exposure to toluene reduces blood testosterone levels in men and male rats in adulthood. We reported that developmental exposure to toluene via maternal inhalation decreases blood testosterone levels and the expression of 3β-HSD, a steroidogenic enzyme involved in testosterone synthesis, in fetal male rats. Our findings suggest that decreased expression of 3β-HSD in the fetal testes is responsible for the reduction of blood testosterone level. The brain has nuclei exhibiting the morphological sex differences, sexually dimorphic nuclei. The SDN-POA, a sexually dimorphic nucleus of the rat brain, is larger and has more neurons in males than in females. We recently found that the volume of the SDN-POA became smaller in male rats exposed to toluene during the perinatal period. We here discuss the effects of developmental exposure to toluene on the sexual differentiation of the brain in rats.
