Figure 2. Actions of isoproterenol on Purkinje fiber (PF) and ventricular muscle (VM) conduction velocity and on conduction time across the Purkinje-ventricular muscle junction (PVJ) in 10 canine papillary muscle preparations. Solid lines = responses in the absence of halothane (-HAL); dashed lines = responses with 0.4 mM halothane (+HAL). The error bars are the least significant difference value such that non-overlapping errors indicate significant (P <or= to 0.05) time-dependent changes or differences - and + HAL at each time based on the overall ANOVA. a = time of onset of response - HAL; b = time of onset of response + HAL.