Figure 2

GABA’s effect on exemplary upper layer pyramidal neuron prior to and following L6/WM stimulation. A: Spike firing of the neuron during passage of transmembrane current – note that inward current elicits spike firing adaptation characteristic of the RS (regularspiking) class of cortical neurons. B: Upper and lower panels show membrane potential alteration induced by each puffer application of GABA before (upper trace) vs. after (lower trace) exposure to the 1 s 20 Hz L6/WM stimulus. Dots beneath each trace – denoted by P – indicate time of each of the GABA puffs applied before (upper trace) and after (lower trace) L6/WM stimulation. Filled rectangle (labeled C) indicates time of L6/WM stimulation. C: Time-course of depolarizing membrane potential response to the first GABA puff after electrical stimulation vs. the hyperpolarizing time-course of GABA puff response before L6/WM stimulation (average over 7 puffs shown in panel B). D: Voltage-clamp recordings showing GABA-evoked transmembrane currents prior to (top trace) and immediately following (bottom trace) L6/WM stimulation. Horizontal bar and dot at bottom indicate period of L6/WM stimulation and GABA puff, respectively. E: Amplitude of the response of each neuron to GABA is plotted as a function of time of each puff in the series of puffs delivered prior to (filled circles) and after (open triangles) L6/WM stimulation. F: Second-order least-squares approximations of the distributions of the GABA responses shown in panel A. Plot indicated by interrupted line shows 2nd order least squares approximation of observations obtained prior to layer VI stimulation (“Before”); plot indicated by bold solid line shows 2nd order least squares approximation of observations obtained after L6/WM stimulation (“After conditioning”). Light solid line labeled “Difference” is the difference between the “Before” and “After” distributions and estimates the time-course of the effect of L6/WM stimulation on the action of GABA.