Genetic analysis of the mu-opioid receptor in alcohol-dependent individuals

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Item Type:	Article
Title:	Genetic analysis of the mu-opioid receptor in alcohol-dependent individuals
Creators Name:	Rommelspacher, H., Smolka, M., Schmidt, L.G., Samochowiec, J. and Hoehe, M.R.
Abstract:	On the basis of various study results, it is suggested that the ethanol-induced activation of the endogenous opioid system may play an important role in mediating the reinforcing effects of ethanol. The mesolimbic dopamine reward system is activated by both ethanol and opioids, and genetic differences in the sensitivity of the endogenous opioid system to alcohol may be an important factor determining the risk for the development of excessive alcohol consumption. Thus, variants of the {mu}-opioid receptor ({mu}OR) gene may confer vulnerability to alcohol dependence. Five exon 1 variants of the μOR were investigated in 327 alcohol-dependent and 340 healthy control subjects. The Val6 variant of the +17C/T polymorphism and the Asp40 variant of the +118A/G polymorphism showed a trend to an increased allele frequency in alcohol-dependent subjects. The latter polymorphism was investigated in more detail. The dopamine receptor agonist apomorphine causes an increase in growth hormone (GH) levels in the blood by stimulating the release of growth hormone-releasing hormone. {beta}-endorphin also activates this regulatory circuit. We found a blunted response in intoxicated alcohol-dependent subjects, but no difference in GH response between the groups of alcohol-dependent subjects with and without the variant Asp allele. However, alcohol-dependent subjects with the Asp allele showed a significantly higher GH response at day 7 after alcohol withdrawal and a tendency to lower novelty seeking. These results suggest to us that there is reduced dopaminergic neuronal activity in alcohol-dependent subjects with the {mu}OR Asp40 allele, along with a compensating increase in dopamine receptor activity. The difference between the two groups of alcohol-dependent subjects can be demonstrated only under certain conditions such as alcohol withdrawal, which necessitates the adaptation of the neurones to a new homeostasis.
Keywords:	{Beta}-Endorphin, {Mu}-Opioid Receptor, Alcohol-Dependent Subjects, Dopamine, Novelty Seeking, Polymorphism
Source:	Alcohol
ISSN:	0741-8329
Publisher:	Elsevier / Pergamon Press
Volume:	24
Number:	2
Page Range:	129-135
Date:	1 January 2001
Official Publication:	https://doi.org/10.1016/S0741-8329(01)00139-2
PubMed:	View item in PubMed

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