Effects of NMDA modulation in scopolamine dementia.

D-Cycloserine is a partial agonist at the strychnine-insensitive neuronal glycine receptor and positively modulates the N-methyl-D-aspartate (NMDA) excitatory amino acid receptor. NMDA receptors appear to be important in learning and memory, and D-cycloserine facilitates learning in rats. In man, central cholinergic blockade due to scopolamine administration impairs attention, information processing, and memory for new information, the latter secondary memory impairments resembling those shown in patients with Alzheimer's disease (AD). D-Cycloserine has been studied for its ability to counteract the cognitive decrements produced by scopolamine in young and elderly healthy volunteers. D-Cycloserine specifically antagonized the memory impairments produced by scopolamine. These findings provide evidence of NMDA receptor involvement in human memory and suggest a novel mechanism for alleviation of memory loss associated with aging and dementia.