Modulation of the behavioural effects of interleukin-1 in mice by nitric oxide.

Interleukin-1 is a cytokine which mediates the host response to infection and inflammation and is responsible for sickness behaviour. Inhibition of nitric oxide synthase activity by N omega nitro-L-Arginine-Methyl-ester (30 mg kg-1, i.p.) potentiated the depressive effects of interleukin-1 (375 ng, i.p.) on social investigation in mice. This effect was attenuated by L-arginine (180 mg kg-1, i.p.) but not by D-arginine. The same treatment did not alter the body weight loss induced by interleukin-1. These results suggest that nitric oxide plays a protective role in the neural effects of interleukin-1.