Selective loss of dopamine D₃-type receptor mRNA expression in parietal and motor cortices of patients with chronic schizophrenia

The expression of dopamine D₃-subtype-receptor mRNA was analyzed in defined anatomic regions of brain obtained postmortem from patients with chronic schizophrenia and from controls. The specific amplification of D₃-encoding cDNA by PCR allowed the identification of D₃ mRNA expression in a wide variety of anatomic regions in both control brains and brains obtained from schizophrenic patients. However, in the parietal cortex (Brodmann areas 1, 2, 3, and 5) and motor cortex (Brodmann area 4), a selective loss of D₃ mRNA expression was found in schizophrenia. A different D₃ mRNA species was identified that appears to be widely expressed and that is still found in those regions of schizophrenic brains where D₃ mRNA could not be detected. Compared with D₃ mRNA this RNA is significantly less abundant, and at present its function (if any) is unclear. Many variables associated with either the course and/or the therapeutic management of the disease may account for the selective loss of D₃ mRNA in the motor, somatosensory, and somatosensory association areas of schizophrenic brains.