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Schizophrenia has been associated with anatomical and functional abnormalities of the dorsolateral prefrontal cortex (DLPFC), which may reflect abnormal connections of DLPFC neurons. We measured mRNA levels of growth-associated protein (GAP-43), a peptide linked to the modifiability of neuronal connections, in post-mortem brain tissue from two cohorts of patients with schizophrenia and controls. Using the RNase protection assay (RPA), we found a significant reduction in GAP-43 mRNA in the DLPFC, but not in the hippocampus, of patients with schizophrenia. With in situ hybridization histo- chemistry (ISHH), performed on a separate cohort, we confirmed the reduction of GAP-43 mRNA in the DLPFC of patients with schizophrenia. We detected reduced GAP-43 mRNA per neuron in layers III, V and VI of patients with schizophrenia compared with normal controls and patients with bipolar disorder. Thus, glutamate neurons in DLPFC of schizophrenic patients may synthesize less GAP-43, which could reflect fewer and/or less modifiable connections than those in normal human brain, and which may be consistent with the deficits of prefrontal cortical function that characterize schizophrenia.

Late onset vacuous chewing movements (VCMs) from chronic neuroleptic treatment have been used as a rat model of tardive dyskinesia (TD). Early onset VCMs have also been observed, raising questions about the validity of this model. To assess the relationship between these two types of VCMs, pharmacological and neurochemical properties of early and late onset VCMs were compared. "Acute" VCMs were induced by daily intraperitoneal injections for 1-21 days. "Tardive" VCMs were induced by intramuscular injections of haloperidol decanoate every 3 weeks for 30 weeks followed by a 24-week withdrawal period. Suppression was attempted for both types of VCMs using several doses of intraperitoneal haloperidol. Striatonigral activation was assessed by measuring mRNA expression levels of the neuropeptides dynorphin and substance P using in situ hybridization histochemistry. Enkephalin mRNA was also measured as an index of striatopallidal activation. The results indicate that acute VCMs cannot be suppressed with increased doses of haloperidol and are associated with reduced dynorphin and substance P. This profile is similar to that seen with an animal model of parkinsonism. Tardive VCMs, in contrast, were markedly suppressed by haloperidol. They have previously been shown to be associated with increased striatonigral activation as indicated by increased dynorphin mRNA. Enkephalin mRNA was elevated following both short and long term treatment. Although superficially similar, acute and tardive VCMs appear to have different pharmacological and neurochemical profiles, suggesting they are related to acute extrapyramidal side effects and tardive dyskinesia, respectively.