Whole-cell patch-clamp recordings of an NMDA receptor-mediated synaptic current in rat hippocampal slices

Whole-cell patch-clamp recordings and pharmacological techniques have been used to obtain low noise recordings of 2 excitatory postsynaptic synaptic currents (termed EPSCA and EPSCB) evoked by stimulation of the Schaffer collateral-commissural pathway in rat hippocampal slices. EPSCA was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and EPSCB was blocked by D-2-amino-5-phosphonovalerate (APV), indicating their mediation by non-N-methyl-D-aspartate (non-NMDA) and NMDA receptors, respectively. EPSCB has a slower time-course than EPSCA and its current-voltage relationship was highly non-linear with a region of negative slope conductance from -35 to -100 mV. These properties of EPSCA and EPSCB can explain their differing participation in synaptic transmission in this pathway.