AII AMACRINE CELLS EXPRESS FUNCTIONAL NMDA RECEPTORS

NMDA and non-NMDA receptors mediate the majority of fast excitatory sy naptic transmission in the CNS. AII amacrine cells in the mammalian re tina receive glutamatergic input from rod bipolar cells and are known to express non-NMDA receptors. We have investigated the expression of NMDA receptors in these cells by recording responses to exogenously ap plied NMDA in whole-cell recordings in slices of rat retina. Most cell s displayed clear responses to NMDA. The responses could be blocked by a specific NMDA receptor antagonist and were characterized by voltage -dependent block with outward rectification. These results suggest tha t NMDA receptors could play a role in mediating excitatory synaptic in put to AII amacrine cells.