Petroff Ognen A C
Department of Neurology, Yale University, New Haven, Connecticut 06520-8018, USA.
Neuroscientist. 2002 Dec;8(6):562-73. doi: 10.1177/1073858402238515.
Cortical excitability reflects a balance between excitation and inhibition. Glutamate is the main excitatory and GABA the main inhibitory neurotransmitter in the mammalian cortex. Changes in glutamate and GABA metabolism may play important roles in the control of cortical excitability. Glutamate is the metabolic precursor of GABA, which can be recycled through the tricarboxylic acid cycle to synthesize glutamate. GABA synthesis is unique among neurotransmitters, having two separate isoforms of the rate-controlling enzyme, glutamic acid decarboxylase. The need for two separate genes on two chromosomes to control GABA synthesis is unexplained. Two metabolites of GABA are present in uniquely high concentrations in the human brain. Homocarnosine and pyrrolidinone have a major impact on GABA metabolism in the human brain. Both of these GABA metabolites have anticonvulsant properties and can have a major impact on cortical excitability.
皮质兴奋性反映了兴奋与抑制之间的平衡。谷氨酸是哺乳动物皮质中的主要兴奋性神经递质，而γ-氨基丁酸（GABA）是主要的抑制性神经递质。谷氨酸和GABA代谢的变化可能在皮质兴奋性的调控中发挥重要作用。谷氨酸是GABA的代谢前体，GABA可通过三羧酸循环进行再循环以合成谷氨酸。GABA合成在神经递质中独具特色，其速率控制酶谷氨酸脱羧酶有两种不同的同工型。在两条染色体上需要两个不同的基因来控制GABA合成，这一点尚无合理的解释。GABA的两种代谢产物在人类大脑中以极高的浓度存在。高肌肽和吡咯烷酮对人类大脑中的GABA代谢有重大影响。这两种GABA代谢产物均具有抗惊厥特性，并且可能对皮质兴奋性产生重大影响。
