Figure 5. Ketamine decreases the probability and frequency of N-methyl-D-aspartate receptor channel opening in cell-attached patches. (A) The steady-state probability of at least one channel being open (Po') was 0.058 +/- 0.015 (n = 13), 0.031 +/- 0.01 (n = 8), and 0.014 +/- 0.007 (n = 5), in the presence of 0 micro Meter, 0.1 micro Meter, and 1 micro Meter ketamine, respectively. (B) The frequency of channel opening (f) decreased from a control value of 13.4 +/- 4.4 s sup -1 to 9.1 +/- 4.11 s sup -1 and 5.95 +/- 2.45 s sup -1 in patches exposed to 0.1 micro Meter and 1.0 micro Meter ketamine, respectively (P < 0.05, by the Mann-Whitney test). (C) The current-voltage relations for single-channel currents recorded in the cell-attached and inside-out configurations are shown. Currents were recorded from the same cell before and after patch excision. Vpipetterefers to the pipette holding potential (the resting potential of the cell is not known, so current amplitude is shown relative to the various pipette potentials). The slope conductance, estimated from the regression lines fitted to the data points for the cell-attached and the inside-out patches were 51 pS and 45 pS, respectively. The resting membrane potential of the cell estimated from the reversal potential of currents recorded in the cell-attached configuration was -70 mV. In the inside-out configuration, currents reversed polarity at 0 mV.