Cell uptake and inhibition studies. (a) Cell uptake studies over 120 min of 18F-SIG343 and 18F-SIG343. Cell uptake inhibition studies of 18F-SIG343 (b) and 18F-SIG353 (c) in the presence of competing σ ligands: (+)-pentazocine, haloperidol, unlabelled SIG343 or SIG353 (5 μM). Results were expressed as percentage of applied dose per 1 × 105 of A375 amelanotic human cells with decay correction (means ± SD, n = 3). *P <0.05 drug treatment versus control (one-way ANOVAs with treatment as a factor, followed by Bonferroni's post hoc tests).