It is possible that a decrease in Dhhc8 expression in anhedonic mice does not play a causal role in MD-like mechanisms but results from other neurochemical changes, such as the over-production of neuronal nitric oxide (nNO), a factor of stress and MDD [21], and NMDA-receptor-mediated excitotoxicity. This evidence concerns the gene ZDHHC8 and Menkes disease.