Glycine transporter-1: a new potential therapeutic target for schizophrenia

The hypofunction hypothesis of glutamatergic neurotransmission via N-methyl-D-aspartate (NMDA) receptors in the pathophysiology of schizophrenia suggests that increasing NMDA receptor function via pharmacological manipulation could provide a new therapeutic strategy for schizophrenia. The glycine modulatory site on NMDA receptor complex is the one of the most attractive therapeutic targets for schizophrenia. One means of enhancing NMDA receptor neurotransmission is to increase the availability of the obligatory co-agonist glycine at modulatory site on the NMDA receptors through the inhibition of glycine transporter-1 (GlyT-1) on glial cells. Some clinical studies have demonstrated that the GlyT-1 inhibitor sarcosine (N-methylglycine) shows antipsychotic activity in patients with schizophrenia. Currently, a number of pharmaceutical companies have been developing novel and selective GlyT-1 inhibitors for the treatment of schizophrenia. A recent double blind phase II study demonstrated that the novel GlyT-1 inhibitor RG1678 has a robust and clinically meaningful effect in patients with schizophrenia. In this article, the author reviews the recent findings on the GlyT-1 as a potential therapeutic target of schizophrenia.