Effects of 7-nitroindazole, a neuronal nitric oxide synthase (nNOS) inhibitor, on locomotor activity and contextual fear conditioning in rats.

The effect of 7-nitroindazole (7-NI), a selective neuronal nitric oxide synthase (nNOS) inhibitor, on contextual fear conditioning in rats was examined. Systemic administration of 7-NI did not affect the acquisition of contextual fear (measured as freezing), but it did reduce locomotor activity and cause a corresponding increase in the expression of contextual freezing. It is concluded that nNOS activity is not required for either the acquisition or expression of contextual fear conditioning.