In summary, we have shown specific disturbances in the glutamatergic post-synaptic density and DRD1 in human heroin abusers in diverse populations. We observe gene-gene interactions between SNPs in these neuronal systems, including a highly significant HOMER1 x DRD1 interaction. This interaction relates significantly to protein expression of HOMER1 in the dorsal striatum, a brain region implicated in habit formation. Future studies will explore the functional role of these DRD1-glutamate interactions in the opiate abuser as well as examine this interaction in other substance abuse populations.
