Figure 6.

Elevated intracellular Na⁺ accelerates recovery from desensitization to paired pulses of AMPH. A, AMPH (10 μm) was applied for 100 ms with a paired-pulse protocol at a variable interval to monitor recovery from desensitization. One representative cell is shown for 90 mm Na⁺ or 0 Na⁺ internal. B, The current in response to the second AMPH application, normalized to the current in response to the first application, is plotted against the time between the applications for 0 mm (open squares) and 90 mm (closed circle) internal Na⁺ (n = 6–9). The time constant (τ) for recovery from desensitization for each Na⁺ concentration was determined by fitting to a single exponential function. C, The time constants are plotted as a function of intracellular Na⁺ concentration (n = 5–9). Inset, The rate of recovery from desensitization (1/τ) correlates with the amplitude of the overshoot current across different intracellular Na⁺ concentrations.