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|Section2= }} Kynurenic acid (KYNA or KYN) is a product of the normal metabolism of amino acid L-tryptophan. It has been shown that kynurenic acid possesses neuroactive activity. It acts as an antiexcitotoxic and anticonvulsant, most likely through acting as an antagonist at excitatory amino acid receptors. Because of this activity, it may influence important neurophysiological and neuropathological processes. As a result, kynurenic acid has been considered for use in therapy in certain neurobiological disorders. Conversely, increased levels of kynurenic acid have also been linked to certain pathological conditions. Kynurenic acid was discovered in 1853 by the German chemist Justus von Liebig in dog urine, which it was apparently named after.〔Liebig, J., Uber Kynurensäure, ''Justus Liebigs Ann. Chem.'', 86: 125-126, 1853.〕 It is formed from L-kynurenine in a reaction catalyzed by the enzyme kynurenine—oxoglutarate transaminase. == Mechanism of action == KYNA has been proposed to act on four targets: * As an antagonist at ionotropic AMPA, NMDA and Kainate glutamate receptors in the concentration range of 0.1-2.5 mM〔Elmslie KS, Yoshikami D. (1985) Effects of kynurenate on root potentials evoked by synaptic activity and amino acids in the frog spinal cord. Brain Res. Mar 25;330(2):265-72.〕 * As a noncompetitive antagonist at the glycine site of the NMDA receptor. * As an antagonist of the α7 nicotinic acetylcholine receptor. However, recently (2011) direct recording of α7 nicotinic acetylcholine receptor currents in adult (noncultured) hippocampal interneurons by the (Cooper laboratory ) 〔Dobelis P., Varnell A., and Donald C. Cooper. "Nicotinic α7 acetylcholine receptor-mediated currents are not modulated by the tryptophan metabolite kynurenic acid in adult hippocampal interneurons. (2011) Nature Precedings 〕 validated a 2009 study that failed to find any blocking effect of kynurenic acid across a wide range of concentrations, thus suggesting that in noncultured, intact preparations from adult animals there is no effect of kynurenic acid on α7 nicotinic acetylcholine receptor currents 〔〔 * As a ligand for the orphan G protein-coupled receptor GPR35. Another tryptophan metabolite, 5-hydroxyindoleacetic acid exerts its effects via the orphan G protein-coupled receptor GPR35 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「kynurenic acid」の詳細全文を読む スポンサード リンク
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