Reproducibility of regional brain metabolic responses to lorazepam.
Changes in regional brain glucose metabolism in response to benzodiazepine agonists have been used as indicators of benzodiazepine-GABA receptor function. The purpose of this study was to assess the reproducibility of these responses.


METHODS
Sixteen healthy right-handed men underwent scanning with PET and [18F]fluorodeoxyglucose (FDG) twice: before placebo and before lorazepam (30 micrograms/kg). The same double FDG procedure was repeated 6-8 wk later on the men to assess test-retest reproducibility.


RESULTS
The regional absolute brain metabolic values obtained during the second evaluation were significantly lower than those obtained from the first evaluation regardless of condition (p < or = 0.001). Lorazepam significantly and consistently decreased both whole-brain metabolism and the magnitude. The regional pattern of the changes were comparable for both studies (12.3% +/- 6.9% and 13.7% +/- 7.4%). Lorazepam effects were the largest in the thalamus (22.2% +/- 8.6% and 22.4% +/- 6.9%) and occipital cortex (19% +/- 8.9% and 21.8% +/- 8.9%). Relative metabolic measures were highly reproducible both for pharmacologic and replication condition.


CONCLUSIONS
This study measured the test-retest reproducibility in regional brain metabolic responses, and although the global and regional metabolic values were significantly lower for the repeated evaluation, the response to lorazepam was highly reproducible.
Wang
G J
GJ
Medical Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Volkow
N D
ND
Overall
J
J
Hitzemann
R J
RJ
Pappas
N
N
Pascani
K
K
Fowler
J S
JS
D000328:Adult; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D003847:Deoxyglucose / Q000031:analogs & derivatives; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008140:Lorazepam / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014055:Tomography, Emission-Computed
D014151:Anti-Anxiety Agents; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D003847:Deoxyglucose; D005947:Glucose; D008140:Lorazepam