Decreased GABAA benzodiazepine binding site densities in postmortem brains of Cloninger type 1 and 2 alcoholics

Ethanol modulates the GABAA receptor to cause sedative, anxiolytic and hypnotic effects that are qualitatively similar to benzodiazepines and barbiturates. The aim of this study was to explore if GABAA receptor density is altered in post-mortem brains of anxiety-prone Cloninger type 1 and socially hostile type 2 alcoholic subtypes when compared to controls. The GABAA binding site density was measured by whole-hemisphere autoradiography with tritium labeled flunitrazepam ([3H]flunitrazepam) from 17 alcoholic (nine type 1, eight type 2) and 10 non-alcoholic post-mortem brains, using cold flumazepam as a competitive ligand. A total of eight specific brain areas were examined. Alcoholics displayed a significantly (p < 0.001, bootstrap type generalizing estimating equations model) reduced [3H]flunitrazepam binding site density when compared to controls. When localized, type 2 alcoholics displayed a significantly (p ≤ 0.05) reduced [3H]flunitrazepam binding site density in the internal globus pallidus, the gyrus dentatus and the hippocampus, whereas type 1 alcoholics differed from controls in the internal globus pallidus and the hippocampus. While previous reports have demonstrated significant alterations in dopaminergic and serotonergic receptors between type 1 and type 2 alcoholics among these same subjects, we observed no statistically significant difference in [3H]flunitrazepam binding site densities between the Cloninger type 1 and type 2 alcoholics.