Fig. 2.
Propofol prolonged the deactivation and increased the peak amplitude of GABA-induced current. A, Three superimposed responses to brief pulses of GABA (1 mm) were recorded from the same patch in the absence and presence of 10 μm propofol. Each trace represents the average of two to three individual traces. Propofol increased the peak amplitude and charge transfer associated with the responses, an effect that was reversed after the washout of propofol. The top trace shows the open tip junctional current. The inset illustrates the slowing of the fast decay by propofol. The time constant of the fast component of a biexponential function was increased by propofol from 2.2 to 3.1 msec (solid lines). B, The bar graph summarizes the effects of propofol on the peak amplitude and the charge transfer of currents recorded from 17 patches. Values were normalized to those obtained under control conditions. A consistent increase in peak current amplitude (8 ± 2%, n = 17, p < 0.01; filled bar) and in charge transfer (62 ± 5%, n = 17, p < 0.01; open bar) was observed. C, Superimposed traces of currents activated by longer (500 msec) pulses of GABA (1 mm) in the absence and presence of propofol (10 μm) are shown. Note that the predominant effect of propofol is to prolong the deactivation. Similar to the results obtained for brief pulses of GABA, the peak current amplitude was increased (shown in inset). A temporal expansion of the currents is shown in the inset. Propofol slows the initial decay of the response. D, Thebar graph illustrates that the time constant of deactivation (τd) was reversibly increased by propofol.