Sigma Receptor 1 Is Preferentially Involved in Modulation of N-Methyl-<i>D</i>-Aspartate Receptor-Mediated Light-Evoked Excitatory Postsynaptic Currents in Rat Retinal Ganglion Cells

Using patch-clamp whole-cell recording, we investigated how activation of the sigma receptor 1 (σR1) modulates light-evoked excitatory postsynaptic currents (eEPSCs) of ganglion cells (GCs) in rat retinal slice preparations. Bath application of the σR1 agonist SKF10047 (SKF) suppressed N-methyl-D-aspartate (NMDA) receptor-mediated eEPSCs at different holding potentials in ON, OFF and ON-OFF GCs, and the effects were blocked when the preparations were pre-incubated with the σR1 antagonist BD1047. In contrast, SKF had no effects on α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated eEPSCs of these GCs. Furthermore, application of SKF did not affect AMPA receptor-mediated miniature EPSCs of GCs, suggesting that activation of σR1 did not change the release of glutamate from bipolar cells. These results suggest that σR1 may be involved in the regulation of output signaling of GCs by preferentially modulating NMDA receptor-mediated eEPSCs of these retinal neurons.