Lang C H, Ajmal M, Baillie A G
Department of Surgery, State University of New York, Stony Brook 11794-8191.
Am J Physiol. 1995 Feb;268(2 Pt 2):R492-7. doi: 10.1152/ajpregu.1995.268.2.R492.
Intracerebroventricular injection of N-methyl-D-aspartate (NMDA) produces hyperglycemia and increases whole body glucose uptake. The purpose of the present study was to determine in rats which tissues are responsible for the elevated rate of glucose disposal. NMDA was injected intracerebroventricularly, and the glucose metabolic rate (Rg) was determined for individual tissues 20-60 min later using 2-deoxy-D-[U-14C]glucose. NMDA decreased Rg in skin, ileum, lung, and liver (30-35%) compared with time-matched control animals. In contrast, Rg in skeletal muscle and heart was increased 150-160%. This increased Rg was not due to an elevation in plasma insulin concentrations. In subsequent studies, the sciatic nerve in one leg was cut 4 h before injection of NMDA. NMDA increased Rg in the gastrocnemius (149%) and soleus (220%) in the innervated leg. However, Rg was not increased after NMDA in contralateral muscles from the denervated limb. Data from a third series of experiments indicated that the NMDA-induced increase in Rg by innervated muscle and its abolition in the denervated muscle were not due to changes in muscle blood flow. The results of the present study indicate that 1) central administration of NMDA increases whole body glucose uptake by preferentially stimulating glucose uptake by skeletal muscle, and 2) the enhanced glucose uptake by muscle is neurally mediated and independent of changes in either the plasma insulin concentration or regional blood flow.
脑室内注射N-甲基-D-天冬氨酸（NMDA）会导致高血糖并增加全身葡萄糖摄取。本研究的目的是确定在大鼠中哪些组织负责葡萄糖处置率的升高。脑室内注射NMDA，20 - 60分钟后使用2-脱氧-D-[U-¹⁴C]葡萄糖测定各个组织的葡萄糖代谢率（Rg）。与时间匹配的对照动物相比，NMDA使皮肤、回肠、肺和肝脏中的Rg降低了30 - 35%。相反，骨骼肌和心脏中的Rg增加了150 - 160%。这种Rg的增加并非由于血浆胰岛素浓度升高所致。在随后的研究中，在注射NMDA前4小时切断一条腿的坐骨神经。NMDA使受神经支配腿的腓肠肌（149%）和比目鱼肌（220%）中的Rg增加。然而，去神经支配肢体对侧肌肉在注射NMDA后Rg并未增加。第三系列实验的数据表明，NMDA诱导的受神经支配肌肉中Rg的增加及其在去神经支配肌肉中的消除并非由于肌肉血流的变化。本研究结果表明：1）NMDA的中枢给药通过优先刺激骨骼肌摄取葡萄糖来增加全身葡萄糖摄取；2）肌肉对葡萄糖摄取的增强是由神经介导的，且与血浆胰岛素浓度或局部血流的变化无关。
