COMT Val108/158Met genotype affects the mu-opioid receptor system in the human brain: Evidence from ligand-binding, G-protein activation and preproenkephalin mRNA expression. - Achim Berthele; Stefan Platzer; Burkard Jochim; Henning Boecker; Andreas Buettner; Bastian Conrad; Matthias Riemenschneider; Thomas R. Tölle (NeuroImage, 2005)