NMDA RECEPTOR ACTIVATION IN THE AGED RAT - ELECTROPHYSIOLOGICAL INVESTIGATIONS IN THE CA1 AREA OF THE HIPPOCAMPAL SLICE EX-VIVO

The effects of aging on activation of N-methyl-D-aspartate (NMDA) rece ptors were studied in the CA1 field of hippocampal slices from young ( 2-4 months old) and aged (25-32 months old) Sprague-Dawley rats with t he use of ex vivo extra-and intracellular electrophysiological recordi ng techniques. No significant age-related changes of the unitary NMDA- receptor mediated excitatory postsynaptic potentials (EPSPs), recorded from the pyramidal cells after stimulation of the stratum radiatum in a magnesium-free medium and isolated in the presence of the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, were found. Simultaneously, the magnitude of synaptic plasticity which involved NM DA receptor activation was not altered. No significant age-related mod ifications in the mechanisms controlling glutamate release and of post synaptic NMDA receptor responsiveness were revealed. Considering the 3 0-40% decrease in NMDA binding sites in the aged hippocampus, our resu lts suggest the occurrence of compensatory mechanisms which are discus sed. (C) 1997 Elsevier Science Inc.