Developmental stage-dependent expression of the zebrafish COMT. The expression of the COMT mRNA at different stages during embryogenesis and larval development onto maturity was analyzed using quantitative real-time PCR. Samples analyzed were unfertilized zebrafish eggs, zebrafish embryos during the zygote period (0-hour post-fertilization (pf)), cleavage period (1-hour pf), blastula period (3-hour pf), gastrula period (6-hour pf), neurula/segmentation period (12-hour pf), pharyngula period (24-hour pf), and hatching period (48- and 72-hour pf), 1, 2, 3, 4-week-old zebrafish larvae, and 3-month-old male or female zebrafish. The zebrafish COMT mRNA levels were quantified in arbitrary units, normalized against β-actin signal, as described in the Materials and Methods. The data represent calculated mean values derived from three experiments. Statistical significance versus the result for the control is indicated by * with p<0.001. The sample size (n) analyzed was 8.