Immunohistochemical localization of gamma-aminobutyric acid(B) receptor inthe hippocampus of subjects with schizophrenia

Recent studies have demonstrated the involvements of gamma-aminobutyric aci d (GABA) neurotransmitter systems in the schizophrenic brain. In order to f urther elucidate the alterations of this system in schizophrenia, we employ ed immunohistochemical techniques and examined the expression and anatomica l distribution of the GABA(B) receptor in the hippocampus of five subjects with schizophrenia and three age-matched controls. In the control hippocamp us, the most intense immunoreactivity was observed in the soma and processe s of multipolar interneurons throughout the hippocampus. Pyramidal cells to o were intensely labeled in their soma and proximal portion of dendrites, a lthough the labeling intensity was varied in each subregion. For example, i n the CA1 subfield, the labeling intensity of pyramidal cells was much less intense than that in the CA3 and CA2 subfields. In the subjects with schiz ophrenia, GABA(B) immunoreactivity was markedly reduced in granule cells as well as in pyramidal cells throughout the CA fields. In interneurons, GABA (B) labeling was relatively preserved compared to that in pyramidal cells. Our findings suggest that in the hippocampus of schizophrenic patients the expression of the GABAB receptor is reduced, and raise the possibility that this reduction contributes to the pathophysiological process in the schizo phrenic brain. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.