SNAP-25 DEFICIT AND HIPPOCAMPAL CONNECTIVITY IN SCHIZOPHRENIA

Regional abnormalities of brain connectivity may be an important subst rate for the expression of schizophrenia, a severe form of mental illn ess. Brain imaging and postmortem morphometric studies indicate hippoc ampal structure is abnormal in schizophrenia. To study molecular compo nents of hippocampal connectivity the presynaptic proteins SNAP-25 and synaptophysin were assayed in postmortem samples. Immunocytochemical studies indicated reduced SNAP-25 immunoreactivity in schizophrenia co mpared to controls, particularly in the terminal fields of entorhinal cortex projections. Although there were no overall changes in synaptop hysin immunoreactivity, in the granule cell layer of the dentate gyrus synaptophysin immunoreactivity was increased in schizophrenia. These results indicate that disconnection of a subset of hippocampal circuit ry from the entorhinal cortex, as well as intrinsic changes in hippoca mpal connectivity, may contribute to the mechanism of illness in schiz ophrenia.