Sodium channel inhibition is a well-precedented mechanism used to treat epilepsy and other hyperexcitability disorders. The established sodium channel blocker and broad-spectrum anticonvulsant, lamotrigine is also effective in the treatment of bipolar disorder, and has been evaluated in patients with schizophrenia. Double-blind placebo-controlled clinical trials found that the drug has potential to reduce cognitive symptoms of the disorder. However, due to compound-related side-effects and the need for dose-titration, a conclusive evaluation of the drug's efficacy in patients with schizophrenia has not been possible. GSK2 and GSK3 are two new, structurally diverse sodium channel blockers with potent anticonvulsant activity. In this series of studies in the rat, we compared the efficacy of the two new molecules to prevent a cognitive deficit induced by the NMDA receptor antagonist, phencyclidine (PCP) in the reversal-learning paradigm in the rat. We also explored the effects of the drugs to prevent brain activation and neurochemica effects of PCP. We found that both GSK2 and GSK3, like lamotrigine, were able to prevent the deficit in reversal learning produced by PCP, thus confirming their potential in the treatment of cognitive symptoms of schizophrenia. However, higher doses than those required for anticonvulsant efficacy of the drugs were needed for activity in the reversal learning model, suggesting a lower therapeutic window relative to mechanism-dependent central side effects for this indication.
- Received January 19, 2011.
- Revision received April 7, 2011.
- Accepted April 7, 2011.
- The American Society for Pharmacology and Experimental Therapeutics