Expression of excitatory amino acid transporter transcripts in the thalamus of subjects with schizophrenia.

Abstract

Recent investigations of schizophrenia have targeted glutamatergic neurotransmission, since phencyclidine, an N-methyl-D-aspartate (NMDA) receptor antagonist, can induce schizophreniform psychosis. The authors previously reported alterations in thalamic NMDA receptor subunit expression in schizophrenia, consistent with the hypothesis that thalamic glutamatergic hypofunction may contribute to the pathophysiology of this illness. In this study they generalized this hypothesis to include other molecules of the glutamate synapse, specifically excitatory amino acid transporters (EAATs), whose normal expression and regulation in the thalamus may also be disrupted in subjects with schizophrenia. In situ hybridization with riboprobes specific for the human excitatory amino acid transporter transcripts EAAT1, EAAT2, and EAAT3 was performed in discrete thalamic nuclei in persons with schizophrenia and comparison subjects. Higher expressions of transcripts encoding EAAT1 and EAAT2, but not EAAT3, were detected in the thalamus of subjects with schizophrenia. These findings support the hypothesis of glutamatergic dysfunction in schizophrenia and suggest that molecules other than glutamate receptors are abnormally expressed in glutamatergic synapses in this illness.