Although space limitations do not permit an exhaustive review, we want to acknowledge studies implicating other genes in ND, including brain-derived neurotrophic factor (BDNF),108, 109 neurotrophic tyrosine kinase, receptor type 2 (NTRK2),110 arrestin, beta 1 (ARRB1),111 MAP3K4,90 SHC3,112 dynamin 1 (DNM1),113 taste receptor type 2, member 38 (TAS2R38),114 amyloid beta precursor protein-binding, family B, member 1 (APBB1),115 PTEN,116 and neuregulin 3 (NRG3).117 It is worth noting that the first five of these genes belong to the MAPK signalling pathway, which was identified as significantly enriched in involvement with four drugs subject to abuse, namely, cocaine, alcohol, opioids, and nicotine.118
