Reversal of LPS‐induced immobility in mice by green tea polyphenols: possible COX‐2 mechanism

An endotoxin (lipopolysaccharide, LPS) is known to activate the hypothalamo–pituitary adrenocortical axis, as well as norepinephrine and indolamine metabolism. Systemically administered LPS produces depression in the forced swimming-induced despair behaviour model in mice. The present study was designed to investigate the effect of green tea extract (GTE) on LPS-induced despair behaviour and to explore the mechanism involved in modulation of LPS-induced immobility by GTE. GTE (10–100 mg/kg) pretreatment reversed LPS-induced immobility in a dose-dependent manner. Rofecoxib (2 mg/kg) and nimesulide (2 mg/kg), COX-2 inhibitors, also reversed the LPS-induced immobility, which was significantly potentiated by concomitant administration of GTE. On the other hand, GTE did not show any potentiating effect on immobility with naproxen (10 mg/kg), which is a nonselective COX blocker. Interestingly the antioxidant, carvedilol (2 mg/kg) did not produce any effect on immobility either in normal or in LPS treated mice. The results of the study implicate the role of COX-2 inhibition by GTE in the reversal of LPS-induced immobility. Copyright © 2004 John Wiley & Sons, Ltd.