The effects of aging on activation of metabotropic glutamate (mGlu) receptors were studied in the CA1 field of hippocampal slices from young (3- to 4-month-old) and aged (24- to 27-month-old) Sprague-Dawley rats with the use of ex vivo electrophysiological recording techniques. The depolarization of membrane potential, the increase in input resistance, and the blockade of the afterhyperpolarization induced in pyramidal cells of young rats by bath application of the mGlu receptor agonist (+/-)-trans-1-aminocyclopentate-1,3-dicarboxylic acid were not altered in aged animals. No age-related changes of the depressive effects of the mGlu receptor agonist were found on either the excitatory glutamatergic postsynaptic potential or the GABA-mediated inhibitory postsynaptic potentials induced by the stimulation of the stratum radiatum. The magnitude of synaptic plasticity involving mGlu receptor activation, although weaker, was not significantly altered in aged rats. This absence of age-related effects on activation of mGlu receptors may be important in understanding the possible origins of the alterations in neuronal plasticity which occur in brain aging.