Figure 3. Percentage of vasodilatation and percentage of change in the calculated cerebral vascular resistance index for measured halothane concentrations of 0.5%, 1.0%, 1.5%, 2.5%, and 4.0%. Percentages of halothane expressed are those calculated from measured artificial cerebrospinal fluid halothane concentrations in the slice chamber. The data are normalized to the amount of constriction produced by prostaglandin F^2alpha. *P < 0.05 versus control, (dagger)P < 0.05 versus immediately lower concentrations.