The serotonergic system in the raphe is a major target of the Hb-IPN circuitry in mammals and fish (Herkenham and Nauta, 1979; Okamoto et al., 2012; Chou et al., 2016) and is involved in depression and anxiety (Ressler and Nemeroff, 2000; McDevitt et al., 2011). This evidence concerns the gene GSTM1 and major depressive disorder.