Altered CB 1 receptor coupling to G-proteins in the post-mortem caudate nucleus and cerebellum of alcoholic subjects

Abstract

Biochemical, pharmacological and genetic evidence suggests the involvement of the endocannabinoid system in alcohol dependence. The aim of the present study was to evaluate the state of CB₁ receptors in post-mortem caudate nucleus, hippocampus and cerebellum of alcoholic subjects.

CB₁ protein levels were measured by Western blot, CB₁ receptor density and affinity by [³H]WIN55,212-2 saturation assays and CB₁ functionality by [³⁵S]GTPγS binding assays. Experiments were performed in samples from 24 subjects classified as non-suicidal alcoholics (n = 6), suicidal alcoholics (n = 6), non-alcoholic suicide victims (n = 6) and control subjects (n = 6).

Alcoholic subjects presented hyperfunctional CB₁ receptors in the caudate nucleus resulting in a higher maximal effect in both alcoholic groups compared to the non-alcoholic groups (p < 0.001). Conversely, in the cerebellum the non-suicidal alcoholic subjects showed hypofunctional receptors with lower maximal effect and potency (p < 0.001). No changes were found in the CB₁ protein expression in either region. In the hippocampus of alcoholic subjects, no changes were observed either in the functionality, density or protein levels.

Our data support an association between endocannabinoid system activity and alcoholism. The modifications reported here could be either a consequence of high lifetime ethanol consumption or a vulnerability factor to develop alcohol addiction.