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-image-aspartate (NMDA) receptors 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 the use of ex vivo extra- and intracellular electrophysiological recording 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 NMDA receptor activation was not altered. No significant age-related modifications in the mechanisms controlling glutamate release and of postsynaptic NMDA receptor responsiveness were revealed. Considering the 30–40% decrease in NMDA binding sites in the aged hippocampus, our results suggest the occurrence of compensatory mechanisms which are discussed.