Gene expression of metabotropic glutamate receptor 5 and excitatory amino acid transporter 2 in the schizophrenic hippocampus

A disturbance in glutamategic transmission has been suggested to contribute to the pathophysiology of schizophrenia and recent studies on ionotropic g lutamate receptors are consistent with altered glutamatergic function in th e hippocampus of schizophrenics. In order to investigate this hypothesis fu rther, the expression of two 'glutamategic' markers, the mRNAs of metabotro pic glutamate receptor 5 (mGluR5) and human excitatory amino acid transport er (EAAT2) were compared in the hippocampus of control subjects and schizop hrenics. We examined the regional/cellular mRNA expression of mGluRS and EA AT2 in postmortem hippocampal sections from schizophrenics and control subj ects, using in situ hybridization. Regions of interests were dentate,gyrus, cornu ammonis 4, 3, 1 and parahippocampal gyrus. The regional/cellular mGl uRS mRNA content was not different between the two groups. The cellular EAA T2 mRNA content was significantly decreased in schizophrenic parahippocampa l gyrus, but not in other hippocampal regions. Furthermore, only in the par ahippocampal gyms, schizophrenics had a significantly increased mGluR5/EAAT 2 ratio at both the regional and cellular mRNA level. The results suggest t hat a disturbance of glutamatergic neurotransmission in schizophrenia was n ot apparent using these indices in the hippocampus, but 'hypo-glutamatergic ' neurotransmission may be present in the schizophrenic parahippocampal gyr us. (C) 2000 Elsevier Science B.V. All rights reserved.