Parameters representing the voltage sensitivity of current flow through NMDA receptors were determined following NMDA application onto pre-identified dorsal horn neurons. (A) NK1R+ neuron in the superficial dorsal horn was selectively labeled by TMR-substance P in a transverse slice (40 × objective). (B) IR-DIC image showing the NK1R+ neuron patched with a pipette. (C) A representative trace shows an NMDA-evoked inward current with 100 μM Mg2+ in the bath. (D) Current responses to voltage ramps are shown at expanded time base. (E) The voltage dependence of NMDA receptor-mediated currents derived from NMDA evoked currents. (F) The same as in Figure E. The conductance of NMDA receptors at -90 mV (g(-90 mV)) and MIC (g(MIC)) are illustrated.