In rodent whole-brain homogenates, haloperidol and loxapine treatments increased AADC mRNA, whereas the second-generation antipsychotic sulpiride (a DRD2 and DRD3 antagonist) did not.55 The differential effects of distinct antipsychotics on AADC gene expression may reduce the ability to detect a consistent change in AADC in post-mortem tissue and exposure to antipsychotics may mask potential changes in AADC in schizophrenia. Here, DRD2 is linked to schizophrenia.