(0.15 %ID/g). 1c showed higher passive permeability than 1f in vitro, which was consistent with the faster brain clearance of [ 18 F]1c compared to [ 18 F]1f. However, preinjection of the OXR antagonist suvorexant did not significantly block [ 18 F]1c or [ 18 F]1f uptake in the rat brain. Pretreatment with cyclosporin A to study the role of Pgp in limiting brain accumulation moderately increased brain uptake of [ 18