This study was performed to investigate whether nitric oxide (NO) precursor (L-arginine), NO donor (S-nitroso-N-acetylpenicillamine, SNAP) and NO synthase inhibitors [NG-nitro-L-arginine-methylester (L-NAME) and NG-nitro-L-arginine (L-NOARG)] modulate morphine-induced anxiolytic effects in the plus-maze. L-Arginine (100, 200 and 300 mg kg–1, i.p.) and SNAP (4, 8 and 10 mg kg–1, i.p.) reduced the anxiolytic effect of morphine (20 mg kg–1, s.c.). L-NAME (10, 20 and 40 mg/kg, i.p.) and L-NOARG (10, 15 and 20 mg kg–1, i.p.) enhanced the anxiolytic effects of morphine (20 mg kg–1, s.c.). On the other hand, L-arginine and SNAP increased the morphine-induced locomotor activity. L-NAME decreased the morphine-induced locomotor activity, but L-NOARG did not modify the morphine-induced locomotor activity. Therefore, these results suggest that the anxiolytic effects of morphine can be modulated by NO systems.

Keywords:
Nitric oxide, Morphine, Anxiety, Plus-maze, Locomotor activity
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© 2003 S. Karger AG, Basel
2003
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