抄録
It has been shown that there are the sex differences in the number of apoptotic cells in the sexually dimorphic nuclei during the development of the brain. We first investigated the developmental changes in apoptotic cell number and their sex differences in the septal area, the antero-ventral peri-ventricular nucleus of the preoptic area (AVPvN-POA) and the sexually dimorphic nucleus of the preoptic area (SDN-POA), and the visual cortex (VC). The sex differences in the apoptotic cell number in the intermediate part of the septal area (LSi), AVPvN-POA, SDN-POA and the VC were found at a specific period for each. The apoptotic cell number in the LSi and the AVPvN-POA were significantly higher in males than those in females on postnatal day (PND) 15 and PND 1, respectively. Those in the SDN-POA and the VC were significantly lower in males on PND 7 and PND 15, respectively. We next tested the effect of maternal exposure to low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic conger of dioxins, on the sex difference in the apoptotic cell number. A single oral administration of 200 ng/kg of TCDD to the dams resulted in the increase in the apoptotic cell number in the VC of their male offspring. TCDD had no effect on the apoptotic cell number in the other nuclei. These results indicate that the maternal exposure to dioxin affect the sex difference in the VC but not in the preoptic area. [Jpn J Physiol 55 Suppl:S38 (2005)]
