[Changes in excitatory amino acids and N-methyl-D-aspartate receptors in the brain in aged mice]

By means of chromatography and radioligand binding assay, changes of excitatory amino acids (EAA) and N-methyl-D-aspartate(NMDA)receptors in the cerebral cortex of aged mice were investigated. It has been demonstrated that the maximal binding capacity (Bmax) of NMDA-sensitive 3H-L-glutamic acid (3H-L-Glu) in the cerebral cortex of aged mice (14 months) was obviously decreased as compared with that of young mice (2 months), but no significant differences in KD values between young and aged mice were observed. The content of L-Glu in the cerebral cortex of aged mice was reduced 18.7% when compared with that of young mice. However, no change in the content of L-aspartic acid was found. Long-term potentiation (LTP) of synaptic transmissions in the hippocampus is mediated by NMDA receptors. We also confirmed that the slope and amplitude of hippocampal population spikes were significantly lower in aged mice than in young mice after induction of LTP by tetanus (100 Hz, ls), and persistent time of LTP in aged mice was shorter as compared with that in young mice. The results showed that the functions of the central EAA neurotransmitter systems are decreased, and such changes may be related to the decline of learning and memory capacities in the aged.