The effects of two enkephalinase inhibitors were studied on the CA1 and dentate hippocampal extracellular field potentials (FPs). The enkephalinase inhibitors thiorphan and SCH 32615, at a concentration of 1-500 microM, failed to significantly affect CA1 and dentate FPs. Thiorphan and SCH 32615, at a concentration of 150 microM, were able to potentiate the enkephalin-induced epileptiform bursting, inducing an increase in the bursting duration and in the number of spikes per burst due to 3.5 microM DAEAM or 0.20 microM DAGO. The results suggest: 1) the potentiation of an electrophysiological opiate receptor-mediated response by enkephalinase inhibitors; 2) the inability to show a direct effect on the basal CA1FP as a result of the inhibition of the endogenous enkephalinase.