Dexamethasone Reduced Clonidine-induced Hypoactivity in Mice

Abstract

Abstract Reduced clonidine anti-nociception in mice given low doses of dexamethasone has encouraged us to investigate the effects of dexamethasone pretreatment on locomotor hypoactivity, another example of clonidine-induced behaviour in mice. Dexamethasone administered intraperitoneally (0.1, 1.0, 10 mg kg−1) 30 min before clonidine reduced clonidine-induced locomotor hypoactivity in the activity cage to an extent which was dose-dependent. Dexamethasone administered centrally (10 ng/mouse) 30 min before clonidine was also able to reduce clonidine-induced locomotor hypoactivity. Cycloheximide administered at a dose of 10 mg kg−1 2 h before clonidine did not change the effects of clonidine but was able to prevent the effects of dexamethasone on clonidine-induced hypoactivity. The glucocorticoid receptor antagonist RU38486 administered centrally at the dose of 1 ng/mouse did not change the effects of clonidine, whereas it was able to block the effects of dexamethasone on clonidine-induced locomotor hypoactivity. These results suggest that the effects of dexamethasone on clonidine-induced locomotor hypoactivity depend on the stimulating effects that dexamethasone exerts on the protein synthesis via the glucocorticoid receptor in the brain.