Immunohistochemical and immunoblot analysis of γ-aminobutyric acid B receptor in the prefrontal cortex of subjects with schizophrenia and bipolar disorder

Immunohistochemical and immunoblot techniques were employed to examine the distribution and expression of GABAB receptors in the prefrontal cortex of postmortem subjects with schizophrenia and bipolar disorder. GABABR1a/b immunoreactivity was observed in the neuronal soma and dendrites as well as in the neuropil in the control subjects. GABABR1a/b immunolabeling in neurons from the subjects with schizophrenia and bipolar disorder was less intense than in those from the control subjects. In control subjects, the distribution of GABABR2 immunoreactivity was found to be similar to that of GABABR1a/b. GABABR2 immunolabeling in neurons from the bipolar disorder group appeared less intense than that of the normal controls as well as that in schizophrenic groups. Immunoblot analysis demonstrated a significant decrease in GABABR1a levels in schizophrenic subjects, while there was a significant decrease in GABABR1a, GABABR1b, and GABABR2 levels in bipolar subjects compared with the controls. The present study suggests that the GABAB receptor is involved in the pathophysiology of schizophrenia and bipolar disorder, and further suggests that the patterns of changes in GABAB receptor subtypes are different between these two disorders.