Hertz Leif, Gibbs Marie E
College of Basic Medical Sciences, China Medical University, Shenyang, China.
J Neurochem. 2009 May;109 Suppl 1:10-6. doi: 10.1111/j.1471-4159.2009.05939.x.
The learning process sets in motion a prolonged, reproducible, and complicated pattern of brain activation, which provides information about biochemical reactions in activated brain. Study of this pattern during one-trial aversive bead discrimination in day-old chick is facilitated by precise timing of sequential metabolic events occurring between a 10-s learning period, in which the chicks learn to associate a red bead with aversive taste, and memory consolidation, indicated by unwillingness to peck at untainted red beads while freely pecking at corresponding blue beads. Inhibition of learning by metabolic inhibitors and restoration of memory by specific substrates at specific times allow determination of specific metabolic events and their neuronal or astrocytic localization. Downstream metabolism of glycogen and of glucose to pyruvate/lactate is segregated into separate pools. Glucose metabolism via pyruvate dehydrogenation provides energy in both neurons and astrocytes and may include gap junction-mediated lactate transport into astrocytes. A key role is played by glycogenolysis, stimulated by beta2-adrenergic and/or 5-HT2-receptor stimulation along with alpha2-adrenergic stimulation of glycogen synthesis. The importance of glycogen reflects that it selectively supports de novo synthesis of transmitter glutamate by combined pyruvate dehydrogenation and carboxylation in astrocytes.
学习过程启动了一种持久、可重复且复杂的大脑激活模式，这种模式提供了有关激活大脑中生化反应的信息。在一日龄雏鸡的单次厌恶性珠子辨别过程中，通过精确计时10秒学习期（在此期间雏鸡学会将红色珠子与厌恶性味道联系起来）和记忆巩固（表现为在自由啄食相应蓝色珠子时不愿啄食未受污染的红色珠子）之间发生的一系列代谢事件，有助于对这种模式进行研究。在特定时间用代谢抑制剂抑制学习并通过特定底物恢复记忆，能够确定特定的代谢事件及其神经元或星形胶质细胞定位。糖原和葡萄糖向丙酮酸/乳酸的下游代谢被分隔到不同的池中。通过丙酮酸脱氢作用的葡萄糖代谢在神经元和星形胶质细胞中都提供能量，并且可能包括通过缝隙连接介导的乳酸转运到星形胶质细胞中。糖原分解起着关键作用，它受到β2-肾上腺素能和/或5-HT2受体刺激以及α2-肾上腺素能对糖原合成的刺激的激发。糖原的重要性体现在它通过星形胶质细胞中丙酮酸脱氢和羧化的联合作用选择性地支持神经递质谷氨酸的从头合成。
