Characterization of glutamate-evoked current responses mediated by NR1/NR2A and NR1/NR2B
| NMDA receptor subunit combination | τDS | τDF | τDφ[Ca2+]e | VrevNa+/K+ | VrevCa2+/K+ | VrevCa2+/K+ + Zn2+ |
|---|---|---|---|---|---|---|
| msec | msec | msec | mV | mV | mV | |
| NR1/NR2A | 651 ± 41 (32) | 148 ± 18 (32) | 770 ± 87 (6) | 5.3 ± 0.8 (57) | 37 ± 3 (3) | 37 ± 2 (3) |
| NR1/NR2B | 715 ± 71 (20) | N.D. | 5.5 ± 1.1 (23) | 38 ± 2 (3) | 39 ± 3 (3) |
All values represent mean ± standard error. The number of different cells used to calculate each value is given in parentheses. N.D., not done. Time constant for agonist-induced current was determined using pCLAMP software. Desensitization of NR1/NR2A currents was best fit to a biexponential curve, giving a fast (τDF) and a slow (τDS) decay, whereas that of NR1/NR2B currents was best fit to a single exponential decay. [CaCl2]e = 1.8 mm. Desensitization of NR1/NR2A currents was best fit by a single exponential curve in nominally Ca2+-free extracellular recording solution ([Ca2+]e). Current-voltage relationships were obtained as described in legend to Fig. 1B. To determine the Ca2+-versus-K+ reversal potential, the extracellular solution was replaced with solution containing high Ca2+ and no Na2+ (see text). The reversal potentials of the two receptor subtypes were not significantly different. The zinc concentration used was 1 μm for NR1/NR2A and 10 μm for NR1/NR2B.