SanﾐYong Niu, CheﾐHui Kuo, Eiichi Taira, Osamu Muraoka,
Yasuyuki Irie, YeﾐHua Gan, Eunju Do and Naomasa Miki*
Department of Pharmacology, Osaka University School of Medicine, Aﾐ6,
2ﾐ2 Yamadaoka, Suita, Osaka 565ﾐ0871, Japan
*To whom correspondence should be addressed.
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ﾐKDa neurofilament (NFﾐ68) gene to the
pGL3ﾐenhancer vector containing a luciferase gene, transfected it into SKﾐNﾐSH
cells and then analyzed transcriptional activity in the cells treated with
agonists or antagonists of opiate receptors. The activity of the NFﾐ68 promoter
was suppressed by naloxone about 55% at 10-5M and 30% at 10-7M
at 48h, but suppressed not by morphine. Naltrexone at 10-5M suppressed
the promoter activity about 20%, but levallorphan, DAMGO, DPDPE and U50488
did not. The inhibition by naloxone was doseﾐdependent and not reversed
by morphine. The inhibitory effect of naloxone was not observed in N18TGﾐ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.
Keywords: Naloxone, Morphine, Promoter, Neurofilament, SKﾐNﾐSH cell