Stress-induced sympathetic activation such as increases in plasma catecholamine levels is crucially integrated in the hypothalamic paraventricular nucleus (PVN). We previously reported that the stress-induced plasma catecholamine responses might be mediated by cyclooxygenase isozymes (COX-1 and COX-2), prostaglandin E₂ and thromboxane A₂ in the brain. In this study, we examined the levels of mRNA expressions for COX-1, COX-2, microsomal prostaglandin E synthase-1 (mPGES-1) and thromboxane A synthase (TxS) in the rat PVN after 6 hours restraint stress (RS). The RS decreased mRNA expressions of COX-1 and TxS, whereas it increased those of COX-2 and mPGES-1. Next we examined the RS-induced nuclear factor κB (NFκB) and IκB-α mRNA expression levels in the PVN. Although RS did not alter the mRNA expression of NFκB, it significantly elevated mRNA expression of IκB-α. Furthermore, intraperitoneal pretreatment of pyrrolidine dithiocarbamate (PDTC), an inhibitor of NFκB, enhanced the decrease in mRNA expressions of COX-1 and TxS, but did not affect those of COX-2 and mPGES-1. The present results suggest that these changes in the mRNA levels in the rat PVN may underlie in the RS-induced sympathetic responses.