Chronic electroconvulsive shock decreases (+/-) 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI)-induced wet-dog shake behaviors of dexamethasone-treated rats

Electroconvulsive shock (ECS) therapy is considered to be an effective treatment for depression, but its mechanism of action is still unknown. We investigated the effect of chronic ECS in rats treated for 14 days with dexamethasone (Dex), a glucocorticoid receptor agonist. Chronic injection of sesame oil decreased body weight change and increased serotonin (5-HT)-2A receptor number and DOI (5-HT-2A, 2C receptor agonist)-induced wet-dog shake (WDS) behaviors. Dex treatment for 14 days decreased body weight of rats, but repeated ECS did not reverse this decrease. Dex also abolished plasma corticosterone levels, and ECS failed to restore these levels. These results indicate that chronic ECS does not antagonize the effect of Dex. The treatment with Dex increased 5-HT-2A receptor binding density of rat frontal cortex and the number of DOI-induced WDS behaviors. Chronic ECS reduced the enhanced WDS behaviors by Dex but had little effect on receptor density. These results suggest that chronic ECS might suppress 5-HT-2A receptor function at the postreceptor signaling level rather than at the receptor itself, without changing HPA axis function in Dex-treated rats.