Fig. 2. Propofol increases the frequency (but not amplitude) of spontaneous excitatory postsynaptic currents (sEPSCs) recorded in mechanically dissociated multipolar ventrolateral preoptic nucleus neurons. ( A ) Increased incidence of sEPSCs during two applications of 10 μm propofol. ( B ) Time course of propofol-induced enhancement of sEPSC frequency (same data as illustrated in A ). ( C ) Averaged traces show only minor change in amplitude, which was not significant (see E ). Overlay of normalized traces indicates no change in sEPSC kinetics in the presence of propofol (10 μm) (n = 30 events). Dose–response relation for propofol-induced changes in sEPSC frequency ( D ) and amplitude ( E ). Solid line in D is least square fit of the frequency data to the Michaelis–Menten equation: P = (PMAX× Cn)/(Cn+ EC50n), where P, PMAX, C, EC50, and n are percent potentiation, maximal potentiation, propofol concentration, concentration of propofol at which the potentiation of sEPSC frequency is 50% of maximum, and the Hill coefficient, respectively. The EC50was 4.2 μm. Each circle represents the mean ± SEM of results from 3 to 14 cells. * P < 0.05, ** P < 0.01 by paired t test for propofol versus prepropofol.