Differential effects of ethanol on plasma catecholamine levels in rats.

Acute ethanol administration (1-4 g/kg, i.p.) had no effect on plasma catecholamine levels in nonstressed animals except at the highest dose where levels of both catecholamines increased. In animals stressed for 30 min, the higher doses had a biphasic effect on plasma catecholamines; at earlier times during stress a reduction in stress-induced increases in both catecholamines was seen, whereas later during stress or after release from stress an increase was noted. Semi-chronic ethanol administration (0.5 and 2 g/kg/day, i.p.) had no significant effect on plasma catecholamine levels in nonstressed rats. In stressed rats, ethanol reduced stress-induced catecholamine increases but these reductions were less than those seen after acute administration. Although ethanol reduced the gross behavioral stress response, no correlation between gross behavioral and biochemical responses was detected. These data show that ethanol can indeed reduce the behavioral and biochemical stress responses in rats but that effects seen depend on the state (nonstressed vs stressed) of the animal, the dose of ethanol (low vs high) used, the length of ethanol administration (acute vs semi-chronic), and the time of measurement of the catecholamine level after ethanol administration.