Research articlePerisylvian GABA levels in schizophrenia and bipolar disorder

- GABAergic neurotransmission is disturbed in histopathological examinations and neuroimaging studies schizophrenia and bipolar disorder.
- Auditory cortices are one of the most relevant brain regions in schizophrenia and bipolar disorder.
- Right hemisphere GABA concentrations were higher in schizophrenia in comparison to the healthy control group.
- GABA concentrations might be altered by several clinical and pharmacological mechanisms in psychiatric disorders.
- GABAergic neurotransmission is prone to rapid changes stimulated by certain dynamics of the receptor, synapse or network.

The aim of this study is to measure GABA levels of perisylvian cortices in schizophrenia and bipolar disorder patients, using proton magnetic resonance spectroscopy (1H-MRS). Patients with schizophrenia (n = 25), bipolar I disorder (BD-I; n = 28) and bipolar II disorder (BD-II; n = 20) were compared with healthy controls (n = 30). 1H-MRS data was acquired using a Siemens 3 T whole body scanner to quantify right and left perisylvian structures' (including superior temporal lobes) GABA levels. Right perisylvian GABA values differed significantly between groups [χ2 = 9.62, df: 3, p = 0.022]. GABA levels were significantly higher in the schizophrenia group compared with the healthy control group (p = 0.002). Furthermore, Chlorpromazine equivalent doses of antipsychotics correlated with right hemisphere GABA levels (r2 = 0.68, p = 0.006, n = 33). GABA levels are elevated in the right hemisphere in patients with schizophrenia in comparison to bipolar disorder and healthy controls. The balance between excitatory and inhibitory controls over the cortical circuits may have direct relationship with GABAergic functions in auditory cortices. In addition, GABA levels may be altered by brain regions of interest, psychotropic medications, and clinical stage in schizophrenia and bipolar disorder.