11-beta-Hydroxysteroid dehydrogenase (11-beta-OHSD) metabolizes corticosterone (B) to inactive 11-dehydrocorticosterone and thus protects the non-specific renal mineralocorticoid receptor from exposure to B in vivo. There is regional 11-beta-OHSD mRNA expression and bioactivity in brain in vitro, but any in vivo function is unknown. We used the [C-14]2-deoxyglucose technique in conscious rats to investigate whether 11-beta-OHSD inhibition with glycyrrhetinic acid alters local cerebral metabolic activity. We found increased glucose use in subregions of the hypothalamus, hippocampus, neocortex and subthalamus. Thus, 11-beta-OHSD may play a role in regulating the effects of B in the brain, in vivo.