CEREBRAL GLUCOSE-METABOLISM DURING PHARMACOLOGICAL STUDIES - TEST-RETEST UNDER PLACEBO CONDITIONS

The reliability of serial [F-18]fluorodeoxyglucose (FDG) PET scans for psychopharmacologic studies was tested by using placebo infusions. Me thods: FDG scans were obtained before and after a 30 min placebo infus ion (n = 10; Group 1) or after each of two bolus infusions with placeb o (n = 8; Group 2). Subjects performed a continuous performance task ( CPT) during each scan. Cardiovascular measures and ratings of anxiety were obtained in all subjects. Samples for determination of plasma nor epinephrine (NE) were taken at multiple time points in Group 1. Result s: A slight increase in apparent global metabolism occurred between sc ans in both Groups 1 and 2. A few regions significantly increased in b oth groups. While an apparent increase in sympathetic activity occurre d during the placebo infusion, neither NE levels, anxiety ratings nor cardiovascular measures correlated with global or regional FDG uptake. Conclusion: Test-retest differences of global and regional glucose me tabolism were highly consistent across two experimental designs. While increases in cerebral glucose metabolism appeared to occur during the second scan, differences between scans were small. This method may of fer advantages for selected psychopharmacologic studies.