Alterations in Plasma Levels of Amino Acids after Intracerebroventricular Administration of L-Serine or D-Serine in Conscious and Freely Moving Rats

Yuko Fujita1, Tamaki Ishima1, Mao Horio1, Hiroko Hagiwara1, 2, Masaomi Iyo2, Kenji Hashimoto*, 1
1 Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba 260-8670, Japan, and
2 Department of Psychiatry, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan

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© 2008 Fujita et al.;

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: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Division of Clinical Neuroscience,Chiba University Center for Forensic Mental Health, 1-8-1 Inohana,Chiba 260-8670, Japan; Tel: +81-43-226-2147; Fax: +81-43-226-2150; E-mail:


L-Serine has a role in cellular proliferation, being a precursor for protein synthesis, and is also important for brain development. D-Serine plays a role as the endogenous co-agonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptors in the brain. Accumulating evidence suggests that abnormality of D-serine levels might be involved in the pathophysiology of schizophrenia. Using the automated blood sampling system, we examined whether or not intracerebroventricular (icv) infusion of L- and D-isomers of serine could affect plasma levels of amino acids in conscious and freely moving rats. The icv infusion of L-serine significantly decreased the plasma levels of glycine, glutamate, and Dserine, but not glutamine and L-serine. Furthermore, the icv infusion of D-serine significantly decreased the plasma levels of glycine, glutamate, and L-serine, but not glutamine. Expectedly, a marked increase of plasma D-serine was detected after icv infusion of D-serine. These findings suggest that the metabolic pathway for L- and D-serine may be markedly different in the rat brain.