Figure 4. (A) Effects of diazepam (10 [micro sign]M), ethanol (20 mM), propofol (0.4 [micro sign]M), halothane (125 [micro sign]M), isoflurane (160 [micro sign]M), enflurane (310 [micro sign]M), pentobarbital (37 [micro sign]M), and ketamine (0.8 [micro sign]M) on the discharge rates in the presence of 0, 20, and 100 [micro sign]M bicuculline. The number of cells tested (without bicuculline/with 20 [micro sign]M bicuculline/with 100 [micro sign]M bicuculline) were: diazepam, 10/8/8; ethanol, 7/7/8; propofol, 8/6/7; halothane, 9/6/6; isoflurane, 10/8/7; enflurane, 9/4/7; pentobarbital, 7/8/8; ketamine, 6/9/5. Statistically significant effects are indicated by asterisks (by t test and analysis of variance, P < 0.05). (B,C) Comparison of the effects of various anesthetics with a drug-free test solution (artificial cerebrospinal fluid) in the presence of 20 [micro sign]M and 100 [micro sign]M bicuculline. When slices were treated with 100 [micro sign]M bicuculline, only pentobarbital and ketamine caused a significant decrease in action potential firing (t test and analysis of variance, P < 0.05). The number of tested cells as in (A). All results are given as mean values +/- SE.