Peripheral injection of dexamethasone modulates anxiety related behaviors in mice: an interaction with opioidergic neurons.

Stress and anxiety initiates a cascade of biochemical and endocrine event which results in behavioral and electrophysiological effects in both animals and humans. In this study, we investigated the effects of dexamethasone (DEX), as a synthetic glucocorticoid, and its interaction with opioidergic system on anxiety related behavior in mice. Young adult male mice were used in this study. A standard elevated plus-maze was used to determine anxiety levels in animal. Different doses of DEX (0.1, 0.5, 1, 2 and 10 mg/kg, SC) or vehicle was injected 30 min before of evaluation. Naloxone (1 and 2 mg/kg, IP) was injected 5 min before the DEX (0.5 and 1 mg/kg) administration. Results indicated that DEX at doses of 0.5 and 1 reduced and in dose of 10 mg/kg increased anxiety related behaviors significantly (P<0.05 in all cases). Also pretreatment of naloxone at doses of 1 and 2 mg/kg attenuated the effects of lower doses of DEX on anxiety related behaviors. Finding above indicated that peripheral administration of glucocorticoids induces biphasic effects on anxiety related behaviors: anxiolytic effects in lower doses and anxiogenic effects in a high dose. Data also revealed an involvement of opioidergic system in anxiolytic effects of glucocorticoids.