Simultaneous measurement of Ca2+ influx and reversal potentials in recombinant N-methyl-D-aspartate receptor channels.

摘要: The Ca(2+) permeability of N-methyl-D-aspartate receptor (NMDA-R) channels was studied in human embryonic kidney cells transfected with the NR1-NR2A subunit combination. To determine fractional current (P(f)), measurements fura-2-based influx and whole-cell currents were made symmetrical monovalent ion concentrations at membrane potentials between -50 mV reversal potential. ratios flux over net charge 2, 5, 10 mM external ([Ca](o)) identical a potential close to component. Assuming unity P(f) this potential, percentage carried by found be 18.5 +/- 1.3% 2 [Ca](o) mV. This value, which is higher than ones reported previously, confirmed independent experiments pure through NMDA-R used calibrate signals. measured values currents, agree predictions Goldman-Hodgkin-Katz equations, are also compatible two-barrier model for permeation, differences energy barriers ions similar on internal sides.