Upregulation of blood-brain barrier (BBB) P-glycoprotein expression causes central nervous system (CNS) pharmacoresistance. However, activation of BBB protein kinase C-β1 (PKC-β1) rapidly reduces basal P-glycoprotein transport activity. We tested whether PKC-β1 activation would reverse CNS drug resistance caused by dioxin acting through aryl hydrocarbon receptor. A selective PKC-β1 agonist abolished the increase in P-glycoprotein activity induced by dioxin in isolated rat brain capillaries and reversed the effect of dioxin on brain uptake of verapamil in dioxin-dosed rats. Thus, targeting BBB PKC-β1 may be an effective strategy to improve drug delivery to the brain, even in drug-resistant individuals.