Alcohol interactions with brain opiate receptors

Ethanol, added $\text{in vitro}$ to mouse caudate membranes, inhibited high-affinity binding of 0.2 nM ³H-dihydromorphine (³H-DHM) over an ethanol concentration range of 250–1,000 mM. At lower, physiologically-attainable ethanol concentrations (e.g.: 50 mM), ³H-DHM binding was significantly increased. Over the concentration range of 50–1,000 mM, ethanol inhibited 0.5 nM ³H-[D-Ala², D-Leu⁵] enkepha l in (³H-ENK) binding to mouse caudate tissue, and no stimulation of Ethanol inhibits opiate binding in a pseudo-competitive manner and, therefore, the concentration of ligand used to assess the effects of ethanol is of major importance. Results obtained with other alcohols which differ in their membrane: water partition coefficients suggest that alcohol effects on opiate binding are not solely dependent on the membrane-disordering properties of the alcohols.