Inhibition by Naloxone of Promoter Activity of the Neurofilament Gene in SK-N-SH Cells

Abstract

Chronic administration of morphine is known to decrease the levels of neurofilaments(NFs)in the ventral tegmental area.We ligated a promoter region of the mouse 68−KDa neurofilament(NF−68)gene to the pGL3−enhancer vector containing a luciferase gene, transfected it into SK−N−SH cells and then analyzed transcriptional activity in the cells treated with agonists or antagonists of opiate receptors.The activity of the NF−68 promoter was suppressed by naloxone about 55% at 10^-5 M and 30% at 10^-7 M at 48h, but suppressed not by morphine.Naltrexone at 10^-5 M suppressed the promoter activity about 20%, but levallorphan, DAMGO, DPDPE and U50488 did not.The inhibition by naloxone was dose−dependent and not reversed by morphine.The inhibitory effect of naloxone was not observed in N18TG−2 cells and PC12 cells.Experiments with various deletion mutants revealed that a region responsible for naloxone suppression spans from −328 to − 101 in the gene.These results suggest that naloxone has the ability to suppress transcriptional activity in some neurons.