Fig. 3.

Na⁺ current is sensitive to preceding voltage fluctuations. A, Voltage-clamp stimulus. The Na⁺ current was measured in response to a brief test pulse to 0 mV after 2 sec of Gaussian voltage fluctuations (bandwidth, 0–50 Hz). A 20 msec recovery period at a holding voltage of −60 mV was imposed between the noise and test pulse. B, Average Na⁺ currents after noise with variances of 0, 25, and 100 mV² are shown. Responses from four pulses after uncorrelated noise stimuli were averaged together to prevent the specific immediate history of the noise from affecting the Na⁺ current.