genotype, one would have concluded a lack of significant difference of HOMER1b/c levels between heroin abusers and controls. Instead, there was a clear inverse relationship as heroin subjects with the T/T genotype at rs265973 of DRD1 had the highest levels of HOMER1b/c expression, while control subjects with this genotype had the lowest expression. It is important to note that we also recently observed dysfunction of HOMER1b/c and DLG4 in the amygdala of heroin abusers.20 HOMER1b/c amygdala levels were increased in drug abusers, but unrelated to genotype in contrast to the striatal findings. The association of DRD1 primarily with striatal HOMER1b/c levels is in line with the well documented modulatory role that dopamine exerts at excitatory synapses in the striatum critical for addiction related behaviors.47,48
