Figure 4. Halothane inhibits muscarinic signaling. All measurements were performed in oocytes voltage clamped at -70 mV. (A) Halothane has a dose-dependent inhibitory effect on Calcium²+-activated Chlorine currents induced by 10 sup -7 M MCh in oocytes expressing the m1 muscarinic receptor. Number of oocytes used for each data point are indicated. *P < 0.01. (B) Inhibition by halothane is reversible. Three consecutive measurements were taken in single oocytes, and data are presented as percent of the control response. CTL = control response; HAL = response in the presence of 0.34 mM halothane; REC = response after recovery. * P < 0.05. (C) Inhibition by 0.34 mM halothane is dependent on MCh concentration. White bars are responses in the absence, black bars in the presence of halothane. * P < 0.01 for 10 sup -7 M MCh, P < 0.05 for 10 sup -6 M MCh.