ホルマリン誘発侵害刺激に対するラット分界条床核のDARPP-32免疫陽性細胞の反応の性差 –pCREB発現を神経活動の指標として

It is widely accepted that females are more sensitive to nociceptive stimuli than males. In the previous study, we showed that there were sex differences in the response of CNS to formalin-induced nociceptive stimuli by checking the expression of phosphorylated cAMP response element-binding protein (pCREB) as a marker of neural activity. In the bed nucleus of the stria terminalis (BST), the number of cells expressing pCREB in female rats was increased 5 min after formalin injection but not in male rats. In the present study, we determined which cells expressed pCREB in response to formalin injection in adult male and female rats. Rats were injected with saline or 2% formalin into the planter surface of the right hindpaw, and they were killed 5 min after the injection. Their brains were served to immunocytochemistry and the number of cells expressing pCREB and dopamine- and cAMP-regulated phosphoprotein (DARPP-32) in the BST was counted. We found that, in females but not in males, the number of DARPP-32 cells expressing pCREB in formalin-injected rats was significantly greater than that in saline-injected rats. The present study suggests that DARPP-32 cells in the BST are at least in part responsible for sex difference in the response of CNS to formalin-induced nociceptive stimuli. [J Physiol Sci. 2006;56 Suppl:S179]