Fig. 5.

Outward charge movement is associated with the glutamate-dependent half-cycle and is not caused by extracellular Na⁺/substrate dissociation. (A) Reverse transport current induced by photolysis of 6 mM MNI-Glu at t = 0 ms (140 mM KMes external). (B and C) Transport currents recorded from the same cell as in A in the reverse exchange mode in the presence of 0.2 mM glutamate and 140 mM (B) and 300 mM Na⁺ (C) external. (D) Relaxation rate constants associated with the rise and decay of the current in the reverse transport and reverse exchange modes. All experiments were done at V = 0 mV. At the top is an illustration of the transport and exchange mode used in these experiments.