Abstract
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, because of 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. (5R)-5-(4-{[(2-Fluorophenyl)methyl]oxy}phenyl)-l-prolinamide (GSK2) and (2R,5R)-2-(4-{[(2-fluorophenyl)methyl]oxy}phenyl)-7-methyl-1,7-diazaspiro[4.4]nonan-6-one (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 N-methyl-d-aspartic acid 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 neurochemical effects of PCP. We found that, like lamotrigine, both GSK2 and GSK3 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.
Footnotes
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.178475.
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- NMDA
- N-methyl-d-aspartic acid
- PCP
- phencyclidine
- CNS
- central nervous system
- DMSO
- dimethyl sulfoxide
- ANOVA
- analysis of variance
- MAO
- monoamine oxidase
- phMRI
- pharmacological magnetic resonance imaging
- MRI
- magnetic resonance imaging
- RARE
- rapid acquisition with refocused echoes
- GSK2
- (5R)-5-(4-{[(2-fluorophenyl)methyl]oxy}phenyl)-l-prolinamide
- GSK3
- (2R,5R)-2-(4-{[(2-fluorophenyl)methyl]oxy}phenyl)-7-methyl-1,7-diazaspiro[4.4]nonan-6-one
- rCBV
- relative cerebral blood volume
- HPMC
- hydroxypropyl-methylcellulose
- VOI
- volume of interest
- mPFC
- medial prefrontal cortex
- 5-HT
- serotonin
- NA
- noradrenaline
- DA
- dopamine
- CGP39653
- d,l-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid.
- Received January 19, 2011.
- Accepted April 7, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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