Abstract : Acute stress affects NMDA receptor (NMDAR)-dependent synaptic plasticity in the CA1 region of the hippocampus, with long-term potentiation and long-term depression (LTD) being, respectively, diminished and facilitated by acute exposure to stress. Here, we examined whether this facilitatory effect of stress on NMDAR-dependent LTD extends to metabotropic glutamate receptor (mGluR)-dependent LTD at Schaffer collateral-CA1 synapses. Application of a low dose (50 microM) of the selective group 1 mGluR agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) promoted LTD in slices from stressed, but not from control, rats. Pretreatment of stressed rats with the glucocorticoid receptor (GR) antagonist RU38486 prevented the facilitation of DHPG-induced LTD (DHPG-LTD), indicating the involvement of corticosterone secretion and, in turn, stimulation of GRs. Finally, pretreatment of slices with an mGluR1, but not an mGluR5, antagonist blunted the sensitizing effect of stress on DHPG-LTD. These results indicate that acute stress, through corticosterone stimulation of GRs, facilitates the expression of mGluR1-dependent DHPG-LTD in the hippocampal CA1 region.
