MEMORY-RELATED CHANGES OF NITRIC-OXIDE SYNTHASE ACTIVITY AND NITRITE LEVEL IN RAT-BRAIN

THE changes of nitric oxide synthase (NOS) activity and nitrite level in rat brain regions after spatial learning were investigated. NOS act ivity was assayed by conversion of [H-3]L-arginine to [H-3]L-citrullin e, and a sensitive fluorometric assay for quantification of nitrite wa s used. Compared with sham-trained rats, NOS activity and nitrite leve l in hippocampus and cortex, and also the nitrite level in cerebellum, was elevated significantly one day after rats had learnt a water-rewa rded spatial alteration task. These results suggest a spatial memory-r elated changes of endogenous NO in rat brain, and support the idea tha t NO participates in learning and memory processes.