DEFICITS IN WATER ESCAPE PERFORMANCE AND ALTERATIONS IN HIPPOCAMPAL CHOLINERGIC MECHANISMS ASSOCIATED WITH NEONATAL MONOSODIUM GLUTAMATE TREATMENT IN MICE

Mice treated neonatally with monosodium glutamate (MSG) were found to have learning and memory deficits in performing a non-spatial water es cape task. Scopolamine impaired the water-escape performance of the co ntrol mice but not that of the MSG-treated mice. It was suggested that the water-escape performance deficit in the MSG-treated mice was a re sult of impaired central cholinergic mechanisms. As such, scopolamine was unable to further incapacitate an already impaired cholinergic sys tem. This is strongly supported by the decreased affinity of the sodiu m-dependent high-affinity choline uptake observed in the hippocampus. D-Cycloserine, a partial agonist at the glycine site of the NMDA recep tor, did not affect the water-escape performance of the MSG-treated an d control mice; nor did it alter the effects of scopolamine. This lack of effect of D-Cycloserine may imply that the NMDA receptors are not involved in non-spatial learning, in contrast to their reported involv ement in spatial learning. (C) 1997 Elsevier Science Inc.