Longevity of synaptic depression in the hippocampal dentate gyrus.

This study used urethane-anesthetized rats to investigate the longevity of heterosynaptically evoked depression of the monosynaptic response generated by synapses between entorhinal cortical (EC) afferents and the cells of the dentate gyrus (DG). Brief, high-frequency activation of the converging ipsilateral EC-DG input depressed the synaptic response of the contralateral EC-DG synapses without prior experimentally induced potentiation. This depression lasted for hours. Such observations are consistent with a role for heterosynaptically induced long-term depression in the encoding functions of synapses.