Figure 1.

NMDA increases conductance in STN neurons. A, I–V plots from an STN neuron recorded using depolarizing voltage ramps before (control) and during (20 μm) application of NMDA. B, Net currents evoked by NMDA, which were calculated by subtracting currents recorded in the control condition from those recorded in NMDA. Data were obtained from the same neuron as shown in A. Note that subtracted NMDA current has a positive slope conductance between voltages of −50 and −80 mV, which is unusual for NMDA-evoked current. C, Current traces recorded during a series of hyperpolarizing voltage steps (from −70 to −140 mV) show that NMDA (20 μm) increases membrane conductance in an STN neuron. Dashed line indicates 0 current. D, Summarized I–V plots showing net (subtracted) currents evoked by NMDA in the control condition (n = 65), in the presence of TTX (0.5 μm; n = 32), and in the presence of AP-5 (50 μm; n = 5,). Note that AP-5 completely blocked NMDA-evoked currents, whereas TTX had no significant effect. Solid lines in these and subsequent I–V plots represent slope conductances that were calculated by linear regression for currents between −70 and −100 mV.