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. Author manuscript; available in PMC: 2009 Mar 1.
Published in final edited form as: Neuropharmacology. 2007 Nov 7;54(3):552–563. doi: 10.1016/j.neuropharm.2007.11.001

Figure 3.

Figure 3

Analysis of propofol actions on miniature IPSCs (mIPSCs). (A) Diary plots of mIPSC event characteristics as recorded from one representative second-order NTS neuron exposed to increasing concentrations of propofol followed by gabazine (GBZ, 3 µM). Tetrodotoxin (TTX; 3 µM) together with NBQX (20 µM) and AP-5 (100 µM) isolated mIPSCs for study. The decay-time constant (top panel), amplitude (second panel) and baseline values (bottom panel) for each detected spontaneous IPSC are displayed (excluding multi-peaked events). All events were counted to establish frequency values (third panel). With increasing propofol exposure, mIPSC duration increased as reflected in the increased decay-time constant and basal holding current shifted to more negative values (inward current). (B) Original experimental trace corresponding to the time of onset of GBZ showing the blockade of phasic mIPSCs but no reversal of baseline holding current to control levels. Broken horizontal lines display the ΔIH from control to 30 µM propofol (−20 pA) in this neuron. (C) An average waveform was generated from mIPSCs for the last 5 minutes for control (0 µM), 1, 3, and 10 µM propofol exposure periods and then fitted with a single exponential at each concentration (left panel). Fits measured the elongation of the decay phase of the mIPSC events with increasing propofol (left panel, 0.3 and 30 µM not shown). Similarly, distributions of decay-time constant values for all individual mIPSCs shifted right with increasing propofol (right panel, 0.3 and 30 µM not shown). (D) Summary aggregate data (n = 10 neurons) for mIPSC events. Measurements were normalized to fractions of the control level within each neuron for decay-time constant, amplitude and frequency before compiling averages. Changes in the baseline holding currents were calculated as changes from control in absolute pA. Dashed lines represent control levels. Aggregate decay-time constant of mIPSCs significantly increased at 3, 10 and 30 µM propofol (*p > 0.05, vs. control, RM ANOVA). Propofol significantly shifted the basal holding current inward compared to control, on average, only at 30 µM propofol (*p > 0.05, vs. control, RM ANOVA). Propofol did not alter either mIPSC amplitudes or their frequency.