Glutamatergic dysfunction in schizophrenia: from basic neuroscience to clinical psychopharmacology

The underlying cellular mechanisms leading to frontal cortical hypofunction (i.e., hypofrontality) in schizophrenia remain unclear. Both hypoactive and hyperreactive prefrontal cortical (PFC) states have been reported in schizophrenia patients. Recent proton magnetic resonance spectroscopy studies revealed that antipsychotic-naïve patients with first psychotic episode exhibit a hyperactive PFC. Conversely, PFC activity seems to be diminished in patients chronically exposed to conventional antipsychotic treatments, an effect that could reflect the therapeutic action as well as some of the impairing side effects induced by long-term blockade of dopamine transmission. In this review, we will provide an evolving picture of the pathophysiology of schizophrenia moving from dopamine to a more glutamatergic-centered hypothesis. We will discuss how alternative antipsychotic strategies may emerge by using drugs that reduce excessive glutamatergic response without altering the balance of synaptic and extrasynaptic normal glutamatergic neurotransmission. Preclinical studies indicate that acamprosate, a FDA approved drug for relapse prevention in detoxified alcoholic patients, reduces the glutamatergic hyperactivity triggered by ethanol withdrawal without depressing normal glutamatergic transmission. Whether this effect is mediated by a direct modulation of NMDA receptors or by antagonism of metabotropic glutamate receptor remains to be determined. We hypothesize that drugs with similar pharmacological actions to acamprosate may provide a better and safer approach to reverse psychotic symptoms and cognitive deficits without altering the balance of excitation and inhibition of the corticolimbic dopamine-PFC system. It is predicted that schizophrenia patients treated with acamprosate-like compounds will not exhibit progressive cortical atrophy associated with the anti-dopaminergic effect of classical antipsychotic exposure.