INHIBITION OF NITRIC-OXIDE SYNTHASE CAUSES ANXIOLYTIC-LIKE BEHAVIOR IN AN ELEVATED PLUS-MAZE

THE action of inhibition of nitric oxide (NO) synthase by N-G-nitro-L- arginine methyl ester (L-NAME) (1- 20 mg kg(-1)) on the exploratory be haviour of rats in the elevated plus-maze was studied. L-NAME induced an anxiolytic-like effect in the plus-maze test, showing a reverse U-s hape action behaviour, with a maximal effect at 10 mg kg(-1). This eff ect was not related to a non-specific increase in motor activity, sinc e in the open field test L-NAME did not affect locomotor activity of r ats. Pretreatment of rats with L-NAME (1-10 mg kg(-1)) also tended to attenuate the anti-exploratory action of CCK agonist caerulein (5 mu g kg(-1)), but this action was not significant. In conclusion, it appea rs that NO may be involved in the process that can lead to anxiety in the rat.