Poly IC (合成2本鎖RNA) は，マウスの自発行動量と脳内のfos発現の変化を引き起こす

Behavioral suppression is a common symptom during viral infection though its mechanism is little understood. In this study, we aimed at establishing a mouse model of virally-induced behavioral suppression, and determining the brain loci possibly involved in behavioral suppression using Fos immunostaining. Spontaneous activity of mice was measured using infrared CCD camera. They were intraperitoneally injected with saline at 17:00-17:30 for 3 consecutive days. On the forth day, they were injected with a viral mimic, polyinosinic-polycytidylic acid (poly IC). Activity of mice was significantly suppressed for 2 days following poly IC. Treatment with diclofenac, a nonselective cyclooxygenase inhibitor, ameliorated behavioral suppression only in the early phase (up to 6 h). After 3 h of poly IC injection, significant increase in Fos expression was observed in several brain loci including ventromedial preoptic area, hypothalamic paraventricular nucl., lateral parabrachial nucl., and nucl. tractus soliatrius. Diclofenac also reduced Fos expression in these brain regions. These results suggest that poly IC-induced behavioral suppression consists of 2 phases, early prostaglandin(PG)-dependent and late PG-independent. Brain loci noted above are possibly involved in PG-dependent behavioral suppression. [J Physiol Sci. 2006;56 Suppl:S241]