Modulation of the stress response by ethanol in the rat frontal cortex

Microdialysis was used to characterize the effects of two doses of ethanol, stress, and their interaction on the dopaminergic system. Saline-treated animals showed no changes in levels of dopamine (DA) or dihydroxyphenylacetic acid (DOPAC). Neither a 0.5- nor a 2-g/kg IP injection of ethanol had an effect on DA or DOPAC in resting animals. Immobilization caused marked increases in DA levels and smaller increases in DOPAC. Pretreatment with 0.5 g/kg ethanol did not reduce the stress-induced increase in DA or DOPAC. However, pretreatment with 2 g/kg ethanol strongly reduced and antagonized the stress-induced increases in DA and potentiated the stress-induced increase in extracellular DOPAC. Our data show that ethanol can have different, dose-dependent effects in resting vs. stressed animals, that it has different effects on DA and DOPAC, and that the high dose antagonized stress-induced increases in DA. The latter adds biochemical evidence to the tension-reduction hypothesis of ethanol by perhaps implicating a reduction in the DA stress response by ethanol as a contributing factor in the development of alcoholism.