However, in contrast to the increases in DRD3 expression in rodents after alcohol and cocaine exposure (Le Foll and Di Ciano, 2015), a very recent study demonstrated that heroin exposure decreased DRD3 expression (Zhu et al, 2016), possibly explaining the apparent reduced efficacy of GSK598809 in those with a primary opiate dependence. This evidence concerns the gene DRD3 and opiate dependence.