Stereospecificity of N-MDA-induced functional deficits

Male Fischer-344N rats were pretreated bilaterally with intrahippocampal (D) (-)-2-amino-7-phosphonoheptanoic acid [(D)-2-APH] (2.5, 5.0 and 10 micrograms/site), a competitive N-methyl-d-aspartate (NMDA) antagonist, prior to the administration of bilateral N-MDA (10 micrograms/site). (D)-2-APH completely attenuated NMDA-induced hyperactivity and water maze acquisition deficits. (D)-2-APH also attenuated hippocampal pyramidal and granule cell loss induced by NMDA. These effects were stereospecific since pretreatment of the isomer L-(+)-2-APH (10 micrograms/site) had no effect on hyperactivity and water maze acquisition deficits produced by NMDA. In addition, (L)-2-APH provided no protection from NMDA-induced hippocampal granule and pyramidal cell loss. Together, these results suggest that the intrahippocampal administration of NMDA might serve as a useful in vivo model for evaluating the effects associated with the overactivation of NMDA receptors.