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. 1999 Dec 15;19(24):10635–10646. doi: 10.1523/JNEUROSCI.19-24-10635.1999

Fig. 4.

Fig. 4.

Propofol reduces slow desensitization. A, Current traces illustrate the response to repetitive applications of brief (3 msec) pulses of GABA (30 pulses administered at a rate of 1 per 3 sec). Under control conditions, the peak amplitude of the current gradually declined to a steady-state level. Propofol reversibly increased the duration of each response and also increased the amplitude of each of the 30 responses to a similar extent. B, A temporal expansion of currents evoked by the 1st and 30th application of GABA is shown. Responses are superimposed, and thearrows indicate the peak amplitude of the 30th response. Note that in the absence or presence of propofol, the decay of the 30th response was accelerated compared with the initial response. This effect is further illustrated in the panel to theright where the peak amplitude is normalized to the maximum response. C, The charge transfer associated with each response during the repetitive applications of GABA is shown. Data points are the average values obtained from seven different patches. After the first two pulses, in the absence of propofol (filled circle), the charge transfer declined monoexponentially with a time constant of 14.4 sec to a steady-state value 39% of the initial response. In the presence of propofol (open circle), the time constant was 15.7 sec, and the steady-state value was 38% of the initial value. The first two data points were not included in the exponential fit. Propofol significantly increased the charge transfer of all 30 pulses to a similar extent (two-way ANOVA, p < 0.01). D, The decline in ton (charge transfer/amplitude) for the 30 pulses activated by GABA is shown. Propofol increased ton of GABA-evoked currents (two-way ANOVA, p < 0.01). The straight line plotted through the last 28 data points represents a linear regression with the slope restricted to zero. The intercept of this line for ton was 90 and 142 msec for currents recorded in the absence and presence of propofol, respectively. Theinset illustrates the calculation of ton.