The current study investigated the expression of neural NOS (nNOS) and the dopamine D2 receptor in the MPOA and PVN after chronic systemic administration of the typical antipsychotic haloperidol, and the atypical antipsychotics risperidone and quetiapine, in which haloperidol and risperidone, but not quetiapine are associated with a high incidence of sexual dysfunction in both humans [22], [23] and rats [9]. This evidence concerns the gene DRD2 and sexual dysfunction.