Glucose is necessary to maintain neurotransmitter homeostasis during synaptic activity in cultured glutamatergic neurons
Glucose is necessary to maintain neurotransmitter homeostasis during synaptic activity in cultured glutamatergic neurons
复制标题
DOI：
10.1038/sj.jcbfm.9600281
复制
发表时间：
2006-10-01
影响因子：
6.3
通讯作者：
Waagepetersen, Helle S.
中科院分区：
文献类型：
--
作者：
Bak, Lasse K.;Schousboe, Arne;Waagepetersen, Helle S.
葡萄糖是成年哺乳动物大脑的主要能量底物。然而，大脑中产生的乳酸也许能够在神经元中发挥这一作用。在本研究中，研究了葡萄糖和乳酸作为维持神经递质动态平衡的底物的相对意义。培养的小脑(主要是谷氨酸能)神经元在含有葡萄糖(2.5 mmoL/L)和乳酸(1或5 mmoL/L)或葡萄糖(2.5 mmoL/L)和[U-C-13]乳酸(1 mmoL/L)的培养液中灌流，并暴露于N-甲基-D-天冬氨酸(300mU/L)脉冲中，导致突触活动，包括囊泡释放。用质谱仪测定细胞内乳酸、丙氨酸、琥珀酸、谷氨酸和天冬氨酸的C-13标记掺入量。[U-C-13]乳酸在非去极化条件下的代谢率高于[U-C-13]葡萄糖，但在诱导去极化过程中显著降低。相反，在两种细胞外乳酸浓度下，在神经元去极化过程中，[U-C-13]葡萄糖的代谢增加。用预负载D[H]天冬氨酸作为谷氨酸示踪剂和DL-苏氨酸-β-苄氧基天冬氨酸抑制谷氨酸转运体，研究了葡萄糖和乳酸作为能量底物在囊泡释放以及转运体介导的谷氨酸内流和外流过程中的作用。结果表明，葡萄糖是防止去极化诱导的转运体(外排)逆转所必需的，而底物的选择不影响囊泡释放。综上所述，本研究表明，在突触活动过程中，葡萄糖是维持神经递质动态平衡的必要底物，突触活动不会导致谷氨酸能神经元乳酸代谢的上调。
Glucose is the primary energy substrate for the adult mammalian brain. However, lactate produced within the brain might be able to serve this purpose in neurons. In the present study, the relative significance of glucose and lactate as substrates to maintain neurotransmitter homeostasis was investigated. Cultured cerebellar (primarily glutamatergic) neurons were superfused in medium containing [U-C-13]glucose (2.5 mmol/L) and lactate (1 or 5 mmol/L) or glucose (2.5 mmol/L) and [U-C-13]lactate (1 mmol/L), and exposed to pulses of N-methyl-D-aspartate (300 mu mol/L), leading to synaptic activity including vesicular release. The incorporation of C-13 label into intracellular lactate, alanine, succinate, glutamate, and aspartate was determined by mass spectrometry. The metabolism of [U-C-13]lactate under non-depolarizing conditions was high compared with that of [U-C-13]glucose; however, it decreased significantly during induced depolarization. In contrast, at both concentrations of extracellular lactate, the metabolism of [U-C-13]glucose was increased during neuronal depolarization. The role of glucose and lactate as energy substrates during vesicular release as well as transporter-mediated influx and efflux of glutamate was examined using preloaded D[3 H]aspartate as a glutamate tracer and DL-threo-beta-benzyloxyaspartate to inhibit glutamate transporters. The results suggest that glucose is essential to prevent depolarization-induced reversal of the transporter (efflux), whereas vesicular release was unaffected by the choice of substrate. In conclusion, the present study shows that glucose is a necessary substrate to maintain neurotransmitter homeostasis during synaptic activity and that synaptic activity does not induce an upregulation of lactate metabolism in glutamatergic neurons.