Aim of this study was to evaluate the expression of the mu-opioid receptor and its ligands (enkephalin/dynorphin) as well as the COMT enzyme in human post mortem brain tissue depending on the genetic COMTVal/Met polymorphism using semi-quantitative immunohistochemistry.
COMTMet/Met homozygosity showed a statistically significant increased expression of the mu-opioid receptor in the mediodorsal nucleus of the thalamus. Concerning the ligand enkephalin an opposite trend was observed. COMTVal/Val homozygosity was associated with a decreased expression of dynorphin A in the nucleus accumbens.
The analysis of COMT expression was opposite to expectations from postulated enzyme activity. COMTMet/Met homozygous showed the highest, COMTVal/Met heterozygous intermediate and COMTVal/Val homozygous the lowest expression levels in the frontal cortex as well as in the striatum, where data were statistically significant.
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