ETHANOL INCREASES DELTA-OPIOID RECEPTOR GENE-EXPRESSION IN NEURONAL CELL-LINES

Long-term treatment with ethanol increases delta-opioid receptor (DOR) expression in the NG108-15 neuroblastoma x glioma hybrid cell line. T o determine the underlying mechanism, we studied the effects of ethano l on [H-3]diprenorphine binding to intact cells and DOR gene expressio n in four related clonal neural cell lines. Incubation with 200 mm eth anol for 48 hr increased [H-3]diprenorphine binding by 1.4- (N18TG2), 1.8- (NG108-15), 1.9- (N4TG1), and 3.0-fold (N 1 E-1 15). Treatment wi th 25, 50, or 100 mm ethanol for 1 week caused a dose-dependent increa se in receptor expression. Receptor up-regulation was associated with an increase in the potency of etorphine for inhibiting prostaglandin E 1-stimulated cAMP accumulation. Constitutive DOR expression differed m ore than 3-fold among the different cell lines and correlated positive ly with basal cAMP levels. Long-term ethanol treatment increased basal cAMP levels in three of the four cell lines, but did not induce cellu lar differentiation. Northern blot analysis demonstrated an identical pattern of multiple transcripts in the four cell lines. Ethanol increa sed the abundance of DOR mRNA by approximately 3-fold in N18TG2 cells and by approximately 5-fold in the remaining cell lines. These finding s indicate that clinically relevant concentrations of ethanol regulate DOR expression by increasing the abundance of DOR mRNA. The disparity between the increase in gene expression and ligand binding suggests t hat ethanol may also modify mRNA translation or receptor processing.