Figure 8. The effects of propofol on miniature inhibitory postsynaptic currents (IPSCs) recorded in supraoptic nucleus slice preparations. (A) A representative trace of IPSCs shows a response to 10^-5M propofol. The holding potential was -70 mV. 6-cyano-7-nitroquinoxaline-2,3-dione (10^-5M) was added to block miniature excitatory postsynaptic currents. The solid horizontal bar indicates the time when 10^-5M propofol was applied. (B) The time course of changes in the amplitude and frequency of IPSCs shown in A. The frequency was determined every 30 s using the peak detection function in Axograph software, version 3.5 (Axon Instruments). The amplitude was an average of the peak currents detected during each 30 s, and the error bars are the SD of the amplitude. The noise level was set as -10 pA and the volley level was set as 50% of the preceding peak. (C and D) Representative traces of IPSCs recorded before and during application of 10^-5M propofol. (E) Dose-response relations of the effects of propofol on the time constant, amplitude, and frequency of miniature IPSCs obtained from 5 (10^-7M), 7 (10^-6M), 8 (10^-5M), and 4 (Intralipid) neurons. The time constant of the decay phase was calculated using a single exponential fit from 17 to 25 synaptic currents randomly selected in each neuron. All three parameters are shown as a percentage change from the average of pre- and postcontrols obtained before and more than 10 min after propofol application. *Significant (P < 0.05) by the Wilcoxon signed-rank test. (F and G) Examples of single exponential fit (dotted line) for IPSCs recorded before and during application of 10^-5M propofol.