title: Targeting kynurenine aminotransferase II in psychiatric diseases: promising effects of an orally active enzyme inhibitor.
abstract: Increased brain levels of the tryptophan metabolite kynurenic acid (KYNA) have been linked to cognitive dysfunctions in schizophrenia and other psychiatric diseases. In the rat, local inhibition of kynurenine aminotransferase II (KAT II), the enzyme responsible for the neosynthesis of readily mobilizable KYNA in the brain, leads to a prompt reduction in extracellular KYNA levels, and secondarily induces an increase in extracellular glutamate, dopamine, and acetylcholine levels in several brain areas. Using microdialysis in unanesthetized, adult rats, we now show that the novel, systemically active KAT II inhibitor BFF-816, applied orally at 30 mg/kg in all experiments, mimics the effects of local enzyme inhibition. No tolerance was seen when animals were treated daily for 5 consecutive days. Behaviorally, daily injections of BFF-816 significantly decreased escape latency in the Morris water maze, indicating improved performance in spatial and contextual memory. Thus, systemically applied BFF-816 constitutes an excellent tool for studying the neurobiology of KYNA and, in particular, for investigating the mechanisms linking KAT II inhibition to changes in glutamatergic, dopaminergic, and cholinergic function in brain physiology and pathology.
authors.affiliation: *To whom correspondence should be addressed; Department of Psychiatry, Maryland Psychiatric Research Center, PO Box 21247, Baltimore, MD 21228, US; tel: 1-410-402-7635, fax: 1-410-747-2434, e-mail: rschwarc@mprc.umaryland.edu.
authors.forename: Hui-Qiu
authors.initials: HQ
authors.lastname: Wu
authors.forename: Masahiro
authors.initials: M
authors.lastname: Okuyama
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kajii
authors.forename: Ana
authors.initials: A
authors.lastname: Pocivavsek
authors.forename: John P
authors.initials: JP
authors.lastname: Bruno
authors.forename: Robert
authors.initials: R
authors.lastname: Schwarcz
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001921:Brain / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D006575:Heterocyclic Compounds, 3-Ring / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012559:Schizophrenia / Q000188:drug therapy; D045162:Thiazolidinediones / Q000008:administration & dosage / Q000494:pharmacology*; D000637:Transaminases / Q000037:antagonists & inhibitors*
chemical_list: C000622260:BFF-816; D004791:Enzyme Inhibitors; D006575:Heterocyclic Compounds, 3-Ring; D045162:Thiazolidinediones; D000637:Transaminases; C021481:kynurenine-oxoglutarate transaminase
keywords: Morris water maze; kynurenic acid; microdialysis; schizophrenia; spatial memory