Noradrenergic involvement in the acute effects of ethanol.

These studies were designed to determine several, possibly related, physiological correlates of an acute dose of ethanol. Male rats were injected with 0.5, 1.0, or 2.5 g/kg of ethanol intraperitoneally, and the accumulation of newly synthesized labeled norepinephrine (from 3H-tyrosine) and of labeled norepinephrine metabolites was examined in several brain regions. Ethanol treatment increased labeled norepinephrine and decreased norepinephrine metabolities in the hypothalamus, brain stem plus midbrain, and telencephalon, without altering endogenous norepinephrine levels. A time course, selected on the basis of previous behavioral studies (Jaffe and Pohorecky, submitted manuscript) on the effects of ethanol on central noradrenergic neurons, disclosed that the accumulation of labeled norepinephrine metabolites was higher than that in saline-injected controls from 30-60 minutes after ethanol injection in the brainstem plus midbrain area, while between 5 and 35 minutes levels were lower than those in control animals. Plasma corticosterone levels were highest 30 minutes after saline injection, while in the ethanol group (1 g/kg) steroids were highest 60 minutes after the injection. Body temperature was significantly decreased only by the 2.5 g/kg dose of ethanol; the hypothermia became evident 50 minutes after an injection of this dosage. We conclude that the brief hypermotile stage produced by a 1 g/kg dose of ethanol (Jaffe and Pohorecky, submitted manuscript) is possibly related to the increased synthesis and release of norepinephrine from central noradrenergic neurons.