Figure 4. (Top) Control dose-related depression of conduction velocity (mean plus/minus SEM, 12 preparations) by epinephrine with 0.7 mM halothane (HAL) in the presence of 0.2 micro Meter propranolol before treatment (6 preparations each) with alpha1-subtype antagonists WB4101 (WB) and chloroethylclonidine (CEC). (Bottom) Dose-response curves for the velocities (mean plus/minus SEM of 2nd-5th-min epinephrine [EPI] values) found before (control [CONT]) and in the presence of 0.5 micro Meter WB4101 or CEC. *P less or equal to 0.05 versus HAL alone. (dagger)P less or equal to 0.01 between groups treated with WB or CEC.