Low doses of ketamine do not alter DA system in zebrafish embryos.

Anesthetic dose of ketamine and ALCAR reduces DA levels and TH gene expression.

ALCAR but not ketamine accelerates DA metabolism but does not alter MAO and COMT gene expression.

Ketamine attenuates MAO gene expression at both sub-anesthetic and anesthetic doses.

Low doses of ketamine as fast-acting anti-depressants may rely on the ability in suppressing the DA metabolizing enzyme, MAO.