Acute ethanol intoxication may not alter alpha 2-adrenoceptors in the human brain

The specific binding of the alpha 2-adrenoceptor agonists [3H]clonidine and [3H]bromoxidine (UK 14304) was measured in the postmortem brain of ethanol intoxicated nonalcoholic subjects (blood ethanol concentration: 1.37 +/- 0.30 g/l) and matched controls. In the frontal cortex, the density of binding sites for [3H]clonidine (Bmax = 58 +/- 7 fmol/mg protein) and [3H]bromoxidine (UK 14304) (Bmax = 49 +/- 7 fmol/mg protein) in ethanol intoxicated subjects did not differ from those in the control groups (Bmax = 68 +/- 4 and 56 +/- 8 fmol/mg protein for the respective radioligand). The dissociation constants (KD) were also similar in both groups. The binding capacities (Bmax) and KD values for both radioligands also were found unchanged in the hypothalamus, amygdala, head of caudate, hippocampus and cerebellum. The results demonstrate that, contrary to the beta-adrenoceptor, the presence of ethanol in the human brain does not alter the high-affinity state of the alpha 2-adrenoceptor in the frontal cortex and possibly also in other brain regions.