Effects of D-Amino Acid Oxidase Inhibitor on the Extracellular D-Alanine Levels and the Efficacy of D-Alanine on Dizocilpine-Induced Prepulse Inhibition Deficits in Mice
Mao Horio1, Yuko Fujita1, Tamaki Ishima1, Masaomi Iyo2, Dana Ferraris3, Takashi Tsukamoto3, Kenji Hashimoto*, 1
Identifiers and Pagination:Year: 2009
First Page: 16
Last Page: 21
Publisher Id: TOCCHEMJ-2-16
Article History:Received Date: 5/3/2009
Revision Received Date: 13/3/2009
Acceptance Date: 17/3/2009
Electronic publication date: 15/4/2009
Collection year: 2009
open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
D-Alanine, one of D-amino acids present in the mammalian brain, is a selective and potent agonist at the Nmethyl- D-aspartate (NMDA) receptors. Like D-serine, D-alanine is reported to be effective in the treatment of schizophrenia. However, orally given D-alanine is metabolized substantially by D-amino acid oxidase (DAAO), diminishing its oral bioavailability. In this study, we studied the effects of oral D-alanine administration with or without the novel DAAO inhibitor, 5-chloro-benzo[d]isoxazol-3-ol (CBIO), on the extracellular D-alanine levels in the brain and on the prepulse inhibition (PPI) deficits after administration of the NMDA receptor antagonist dizocilpine. Co-administration of CBIO (30 mg/kg) with D-alanine (100 mg/kg), but not D-alanine (100 mg/kg) alone, significantly attenuated dizocilpine (0.1 mg/kg)-induced PPI deficits in mice. The in vivo microdialysis study of the conscious and free moving mice revealed that co-administration of CBIO (30 mg/kg) significantly increased extracellular levels of D-alanine in the frontal cortex after oral administration of D-alanine (100 mg/kg). These findings suggest that co-administration of CBIO can increase the bioavailability of D-alanine after oral administration of D-alanine, and that co-administration of CBIO can enhance the efficacy of D-alanine on dizocilpine-induced PPI deficits. Therefore, combination of D-alanine and a DAAO inhibitor such as CBIO offers new therapeutic potential for treatment of schizophrenia.