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The action of inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME) (1-20 mg kg-1) on the exploratory behaviour 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-shape action behaviour, with a maximal effect at 10 mg kg-1. This effect was not related to a non-specific increase in motor activity, since in the open field test L-NAME did not affect locomotor activity of rats. Pretreatment of rats with L-NAME (1-10 mg kg-1) also tended to attenuate the anti-exploratory action of CCK agonist caerulein (5 micrograms kg-1), but this action was not significant. In conclusion, it appears that NO may be involved in the process that can lead to anxiety in the rat.

The action of inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME) (1-20 mg kg-1) on the exploratory behaviour 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-shape action behaviour, with a maximal effect at 10 mg kg-1. This effect was not related to a non-specific increase in motor activity, since in the open field test L-NAME did not affect locomotor activity of rats. Pretreatment of rats with L-NAME (1-10 mg kg-1) also tended to attenuate the anti-exploratory action of CCK agonist caerulein (5 micrograms kg-1), but this action was not significant. In conclusion, it appears that NO may be involved in the process that can lead to anxiety in the rat.