NITRIC-OXIDE SYNTHASE INHIBITORS IMPAIR REFERENCE MEMORY FORMATION INA RADIAL-ARM MAZE TASK IN RATS

We investigated the role of nitric oxide (NO) in learning and memory f ormation in a radial maze test, by using the NO synthase (NOS) inhibit ors, N-G-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7 -NI), and an NO precursor, L-arginine. Rats were trained on a working and reference memory task in an eight arm radial maze for 30 days, whe rein the same four arms were baited for each daily training trial. Dai ly administration of the specific neuronal NOS inhibitor 7-NI, as well as the non-selective NOS inhibitor L-NAME, impaired the acquisition o f the task. Analysis of memory categories affected by NOS inhibitors r evealed that reference memory formation was impaired by the treatment with L-NAME and 7-NI. L-NAME also impaired working memory although 7-N I had no effect. L-Arginine significantly increased the choice accurac y, by reducing the reference memory errors, of the radial arm maze tas k during the last ten days although it had no effect during the first 20 trials. These results suggest that NO plays an important role in sp atial reference memory formation. (C) 1998 Elsevier Science Ltd. All r ights reserved.