Cyclic AMP and beta-adrenergic receptors during the development of physical dependence on ethanol in the rat

The combined effects of chronic ethanol/desipramine treatment on beta-adrenoceptor density and coupling efficiency in rat brain

Both ethanol and desipramine influence beta-adrenoceptor regulation. We reported previously that ethanol partially counteracted desipramine's effects on beta-adrenoceptor. Previous studies utilized beta-adrenoceptor radioligands that also bind to 5-HT1B receptors, thus, changes in 5-HT1B receptors could have confounded the results. The effects of chronic ethanol, desipramine and ethanol/desipramine treatment on beta-adrenoceptor coupling efficiency to Gs protein in rat brain were examined using 125I-iodocyanopindolol after blocking binding to 5-HT1B receptors. In the frontal cortex, ethanol uncoupled beta-adrenoceptor from GS. Desipramine decreased beta-adrenoceptor density, particularly in the high-conformational state, with no effect on coupling. In combined treatment, desipramine prevented ethanol-induced uncoupling. In the hippocampus, desipramine enhanced beta-adrenoceptor coupling, but ethanol had no effect. In combination with desipramine, ethanol enhanced desipramine-induced decrease in beta-adrenoceptor density in the high-conformational state, but uncoupled beta-adrenoceptors, an effect not observed with ethanol alone. These results suggest a complex interplay between ethanol and antidepressants in modulating beta-adrenoceptor function.

Human leukocyte beta-adrenergic stimulated cyclic AMP in ethanol intoxication and withdrawal

The effects of ethanol were examined on cyclic AMP production in intact human leukocytes in vitro. In leukocytes isolated from alcohol abstinent subjects, ethanol enhances isoproterenol-stimulated and prostaglandin E1-stimulated cyclic AMP formation. Without agonist, ethanol is able to stimulate cyclic AMP production at concentrations of 160 mM and above. Leukocytes isolated from subjects undergoing alcohol detoxification showed increases in basal levels of leukocyte cyclic AMP, in isoproterenol-stimulated cyclic AMP, and in ethanol-stimulated cyclic AMP on the 2nd or 3rd day of withdrawal in comparison to the first day of withdrawal and in comparison to abstinent subjects. The data suggest that increased beta-adrenergic activity seen in alcohol withdrawal may be in part due to an increased responsiveness of beta-adrenergic stimulated cyclic AMP in tissues.