Acute and chronic ethanol treatment changes endorphin levels in brain and pituitary.

Acute ethanol administration increased methionine-enkephalin (met-enkephalin) and beta-endorphin levels in distinct areas of the rat brain, whereas chronically supplied ethanol caused a depression of met-enkephalin and beta-endorphin levels in most of the brain areas investigated. The beta-endorphin content of the intermediate/posterior lobe of the pituitary of rats and guinea pigs decreased by 70%. Withdrawal of ethanol resulted in a complete recovery of endorphin levels in brain and pituitary within two weeks. Whether the observed alterations in endorphin concentrations are causally related to the primary mechanisms underlying alcohol dependence is uncertain, since no obvious signs of physical dependence were observed in treated animals.