Differential hippocampal expression of glutamic acid decarboxylase 65 and 67 messenger RNA in bipolar disorder and schizophrenia.

Background: Expression of messenger RNA (mRNA) for the gamma-aminobutyric acid (GABA)-synthesizing enzyme, glutamic acid decarboxylase (GAD), in the prefrontal cortex and the number of GABAergic neurons in the hippocampus are reduced in schizophrenia and bipolar disorder. We tested the hypothesis that the expression of the 2 isoforms, one 65 kd (GAD(65)) and the other 67 kd (GAD(67)), is differentially affected in the hippocampus in schizophrenia and bipolar disorder.

Methods: Hippocampal sections from 15 subjects in 3 groups (control subjects and subjects with schizophrenia and bipolar disorder) were studied using an in situ hybridization protocol with sulfur 35-labeled complementary riboprobes for GAD(65) and GAD(67) mRNA.