Relative mRNA expression, enzymatic activity, and protein expression levels of reference and alternative COMT isoforms and their allelic variants. Fold change in relative mRNA expression level of (A) S-COMT and its alternative counterparts (a)S-COMT-G and (a)S-COMT-A, and of (B) MB-COMT and its alternative counterparts (a)MB-COMT-G and (a)MB-COMT-A. Enzymatic activity with DHBA (normalized to mRNA amount) of (C) of S-COMT and its alternative counterparts (a)S-COMT-G and (a)S-COMT-A, and of (D) MB-COMT and its alternative counterparts (a)MB-COMT-G and (a)MB-COMT-A. Enzymatic activity with DHBA of (E) (a)S-COMT and (F) (a)MB-COMT isoforms only, as extracted from (C) and (D). Protein expression of (G) (a)S-COMT and (H) (a)MB-COMT isoforms. Data are expressed as mean 6 SEM. *P < 0.05, **P < 0.01, ****P < 0.001, and ****P < 0.0001.