After injection of [ 18 F]1c in rats, a maximum brain uptake of 0.17 %ID/g was observed at about 40 sec p.i., whereas preinjection of suvorexant or cyclosporine A both induced increased brain uptake to 0.25 %ID/g (Figure ). [ 18 ]1f could be substrates of the P-gp transporter, as P-gp inhibition by cyclosporine-A could also explain increased brain uptake.