Propofol combined with diazepam synergistically potentiates the GABA-activated chloride current in rat sensory neurons

To investigate the effect of propofol combined with diazepam on the γ-aminobutyric acid (GABA)-activated chloride current (I GABA ) evoked in rat sensory neurons Methods Whole cell patch clamp recordings were made from cultured rat dorsal root ganglionic neurons GABA (3*!μmol/L) was applied by pressure ejection The anesthetics were dissolved in the external solution and given by the “Y-tube' method Results Co-application of propofol (0 3-3*!μmol/L) and diazepam (100*!nmol/L) potentiated the I GABA which was significantly larger than the sum of that potentiated by drug alone Diazepam (100*!nmol/L) shifted the concentration-response curve for the I GABA potentiation induced by propofol to the left in a parallel fashion The EC 50 value for propofol was decreased by diazepam from 7 6±1 8 *!μmol/L to 3 9±1 1*!μmol/L (n=9) Conclusions Our results suggest that propofol combined with diazepam synergistically potentiates the I GABA Diazepam-induced increase in the apparent binding affinity of propofol for the GABA A receptors is likely responsible for a clinical synergistic hypnotic action during co-application with propofol and diazepam