THE ABILITY OF AGED RATS TO SUSTAIN LONG-TERM POTENTIATION IS RESTORED WHEN THE AGE-RELATED DECREASE IN MEMBRANE ARACHIDONIC-ACID CONCENTRATION IS REVERSED

The ability of aged rats to sustain long-term potentiation in the dent ate gyrus of the hippocampus is impaired and this impairment correlate s with decreased release of glutamate and a decrease in membrane arach idonic acid concentration. Twenty-two-month-old rats receiving a diet supplemented with arachidonic acid and its precursor, gamma-linolenic acid, sustained long-term potentiation in a manner indistinguishable f rom four-month-old controls. Dietary supplementation also restored ara chidonic acid concentrations in membranes prepared from hippocampus of these aged animals to levels observed in hippocampus of four-month-ol d rats. Glutamate release stimulated by depolarization was similar in dentate gyrus prepared from young rats and aged rats which received th e experimental diet, but was markedly reduced in aged animals which re ceived the control diet. In addition, the synergism between arachidoni c acid and the metabotropic glutamate receptor agonist, trans-1-amino- cyclopentyl-1,3-dicarboxylate, on glutamate release, which was observe d in hippocampal synaptosomes prepared from four-month-old rats, was a lso observed in hippocampal preparations obtained from aged rats which had been fed with the experimental diet, bur was absent in hippocampa l preparations obtained from aged animals which were fed with control diet. Thus, reversing the age-related decrease in membrane arachidonic acid concentration restored ability of aged animals to sustain long-t erm potentiation and reversed age-related changes in glutamate release . (C) 1997 IBRO. Published by Elsevier Science Ltd.