Anxiolytic-like effects of 7-nitroindazole in the rat plus-maze test

It is considered that nitric oxide (NO) is one of the most interesting rese arch subjects. Because the actual role of NO in the mechanism of anxiety is still unclear, in this study, the involvement of NO in the mechanism of an xiety was investigated, using the plus-maze test. 7-Nitroindazole (7-NI) (1 5, 30, 60, 90, and 120 mg/kg), a new nitric oxide synthase (NOS) inhibitor was studied. The time spent on open arms and open-arm visits was evaluated. 7-NI, at 15-120 mg/kg doses potently increased the time spent on open arms and open-arm visits. However, at 120 mg/kg it attenuated the time spent on the open arms, compared to at 90 mg/kg. This effect was attributed to decr eased locomotor activity in the higher dose group. Neither L-arginine, nor D-arginine (100 mg/kg) significantly affected any of the behavioral paramet ers measured in the rat elevated plus-maze test. Neither drugs revealed any effect on locomotion. L-Arginine but not D-arginine given 10 min before 7- NI, reversed the 7-NI induced anxiolytic-like effects. These data support a n involvement of NO in the process of anxiety, and further suggest that the anxiolytic-like effect of 7-NI may be attributable to the inhibition of NO synthesis. (C) 2000 Elsevier Science Inc.