Effect of central and continuous intravenous injection of interleukin-1 beta on brain c-fos expression in the rat: involvement of prostaglandins.

Utilizing immunohistochemistry for the c-fos protein to detect neuronal activity, we examined the effects of continuous intravenous and intracerebroventricular infusion of interleukin (IL)-1 beta in the rat brain, and the involvement of prostaglandins (PGs) in IL-1 beta-induced c-fos expression. Continuous intravenous infusion of IL-1 beta (10 ng/min) markedly augmented c-fos expression in the paraventricular (PVN) and the supraoptic (SON) nuclei of the hypothalamus as well as in the central amygdaloid nucleus (CeA). The number of IL-1 beta-induced c-fos-positive cells in the PVN and SON was significantly lower in rats pretreated with indomethacin than in vehicle-treated rats. However, the number of IL-1 beta-induced c-fos-positive cells in the CeA remained unchanged. c-fos protein was induced after intracerebroventricular infusion of IL-1 beta (200 ng) in the PVN, SON, and arcuate nuclei of the hypothalamus, and in the CeA. The induction of c-fos immunoreactivity by central administration of IL-1 beta was blocked by indomethacin (500 micrograms/rat), except in the CeA. These findings suggest that PGs are involved in the complex transmission of signals from circulating or central IL-1 beta to hypothalamic neurons.