NITRIC-OXIDE FORMATION DOES NOT UNDERLIE THE MEMORY DEFICITS PRODUCEDBY IBOTENATE INJECTIONS INTO THE NUCLEUS BASALIS OF RATS

Basal forebrain (BF) injections of ibotenic (IBO) acid impair memory, whereas quisqualic (QUIS) acid injections do not. The authors investig ated whether the cytotoxicity and differential behavioral effects of I BO and QUIS in rats depend on the generation of nitric oxide (NO). Inj ections of IBO or sodium nitroprusside (NP), but not QUIS, significant ly increased BF NO formation, as determined by guanosine 3,5-cyclic mo nophosphate levels. IBO, alone or coinjected with methylene blue (MB), and QUIS, alone or coinjected with NP, decreased cortical choline ace tyltransferase (ChAT) activity and the number of ChAT-positive BF neur ons. The BF levels of galanin or neuropeptide Y were unchanged in all lesion groups. QUIS; but not IBO, dose-dependently destroyed NO-produc ing BF cells. Injections of IBO, with or without MB, impaired choice a ccuracy in a T-maze alternation task. The results suggest that the gen eration of NO in the BF does not underlie the spatial working memory d eficit produced by IBO.