BASIC SCIENCE INVESTIGATIONS Intense 18F-FDG Uptake in Brown Fat Can Be Reduced Pharmacologically

Physiologic 18F-FDG uptake in areas of supraclavicular fat in hu-mans (“USA-Fat”) has recently been recognized as 18F-FDG up-take in apparent brown adipose tissue (BAT) using fused PET/CT technology. In this study, we evaluated 18F-FDG uptake in BAT of rats to determine whether pharmacologic or physiologic interven-tions affect the uptake, knowing that BAT has a high density of adrenergic innervation. Methods: Seven- to 8-wk-old female Lewis rats receiving intravenous 18F-FDG injections were exam-ined under various conditions to evaluate 18F-FDG biodistribution into interscapular BAT and major organs. In series 1, rats were given ketamine-based anesthesia or were exposed to cold (4°C for 4 h) to determine whether these interventions increased 18F-FDG uptake in BAT. In series 2, anesthetized rats (ketamine-based anesthesia) were given propranolol, reserpine, or diazepam intra-peritoneally before 18F-FDG injection to determine whether th