Detection and quantification of hippocampal synaptophysin messenger RNA inschizophrenia using autoclaved, formalin-fixed, paraffin wax-embedded sections

Most in situ hybridization histochemistry studies of messenger RNA in human brain have been carried out on frozen tissue. Recently, autoclaving has be en reported to enable routinely processsed material to be used for in situ localization of messenger RNA. We have investigated whether autoclaving als o permits in situ hybridization histochemistry to be used quantitatively. T o do this, we targeted synaptophysin messenger RNA with a S-35-labelled oli gonucleotide probe in autoclaved, formalin-fixed, paraffin wax-embedded sec tions of the hippocampal formation of 11 schizophrenics and ii controls. We compared the results with those seen on frozen sections from adjacent bloc ks, which had been used previously to demonstrate a loss of the messenger R NA in schizophrenia. Synaptophysin messenger RNA was readily detected in th e autoclaved sections. The hybridization signal correlated strongly with th at seen in the frozen sections. We found a similar pattern and magnitude of decreased synaptophysin messenger RNA in schizophrenia in the autoclaved s ections as we had in the frozen sections, including the selective preservat ion of synaptophysin messenger RNA in CA1. The reduction of synaptophysin m essenger RNA was replicated when six subjects with schizophrenia not includ ed in the earlier study were considered separately. We conclude that autoclaving renders formalin-fixed, paraffin wax-embedded sections of human brain suitable for quantitative iii? situ hybridization h istochemistry. This has considerable implications, given the wider availabi lity, better morphology and easier handling of fixed than frozen human brai n tissue. Using this material, we confirmed the finding of decreased synapt ophysin messenger RNA in the hippocampal formation in schizophrenia, furthe ring the evidence for synaptic pathology in this region in the disorder. (C ) 1999 IBRO. Published by Elsevier Science Ltd.