DRD2 and cocaine dependence: Similarly, genes that are suggestive of cocaine addiction (KEGG ID: mmu05030) were upregulated in the HFD group compared with the STD group, but the expression of genes that are involved in these pathways (Th/Slc18a2/Drd2) were downregulated (or tempered) in the HF1G group (p = 0.01).