Effects of putative cognition enhancers on the NMDA receptor by [3H]MK801 binding

Piracetam, aniracetam, and D-cycloserine were tested for their ability to reduce inhibition of [3H]MK801 (dizocilpine) binding by 100 microM kynurenate. Piracetam (100 microM-1 mM) failed to reduce inhibition by kynurenate but stimulated [3H]MK801 binding in the absence of kynurenate. In contrast, D-cycloserine (30 microM-1 mM) and aniracetam markedly reduced this inhibition by kynurenate. Thus, cognition enhancers might function via at least some subtypes of NMDA receptors.