mGluR1/5 receptor densities in the brains of alcoholic subjects: A whole-hemisphere autoradiography study

Increased glutamatergic neurotransmission and hyper-excitability during alcoholic withdrawal and abstinence are associated with increased risk for relapse, in addition to compensatory changes in the glutamatergic system during chronic alcohol intake. Type 5 metabotropic glutamate receptor (mGlur5) is abundant in brain regions known to be involved in drug reinforcement, yet very little has been published on mGluR1/5 expression in alcoholics. We evaluated the densities of mGluR1/5 binding in the hippocampus and striatum of post-mortem human brains by using [3H]Quisqualic acid as a radioligand in whole hemispheric autoradiography of Cloninger type 1 (n=9) and 2 (n=8) alcoholics and healthy controls (n=10). We observed a 30–40% higher mGluR1/5 binding density in the CA2 area of hippocampus in type 1 alcoholics when compared with either type 2 alcoholics or healthy subjects. Although preliminary, and from a relatively small number of subjects from these diagnostic groups, these results suggest that the mGluR1/5 receptors may be increased in type 1 alcoholics in certain brain areas.