Nonsteroidal anti-inflammatory drug, indomethacin improves spatial memory and NMDA receptor function in aged animals

A redox-mediated decrease in N-methyl-D-aspartate (NMDA) receptor function contributes to psychiatric diseases and impaired cognition during aging. Inflammation provides a potential source of reactive oxygen species for inducing NMDA receptor hypofunction. The present study tested the hypothesis that the nonsteroidal anti-inflammatory drug indomethacin, which improves spatial episodic memory in aging rats, would enhance NMDA receptor function through a shift in the redox state. Male F344 young and aged rats were prescreened using a 1-day version of the water maze task. Animals were then treated with the indomethacin or vehicle, delivered in a frozen milk treat (orally, twice per day, 18 days), and retested on the water maze. Indomethacin treatment enhanced water maze performance. Hippocampal slices were prepared for examination of CA3-CA1 synaptic responses, long-term potentiation, and NMDA receptor-mediated synaptic responses. No effect of treatment was observed for the total synaptic response. Long-term potentiation magnitude and NMDA receptor input-output curves were enhanced for aged indomethacin-treated animals. To examine redox regulation of NMDA receptors, a second group of aged animals was treated with indomethacin or vehicle, and the effect of the reducing agent, dithiothreitol ([DTT], 0.5 mM) on NMDA receptor-mediated synaptic responses was evaluated. As expected, DTT increased the NMDA receptor response and the effect of DTT was reduced by indomethacin treatment. The results indicate that indomethacin acted to diminish the age-related and redox-mediated NMDA receptor hypofunction and suggest that inflammation contributes to cognitive impairment through an increase in redox stress.