Jeftinija S, Jeftinija K, Liu F, Skilling S R, Smullin D H, Larson A A
Department of Veterinary Anatomy and Neuroscience Program, Iowa State University, Ames 50011.
Neurosci Lett. 1991 Apr 29;125(2):191-4. doi: 10.1016/0304-3940(91)90025-o.
Multiple lines of evidence implicate the excitatory amino acids (EAAs) (L-aspartate (L-Asp) and L-glutamate (L-Glu) as excitatory transmitters in the spinal cord. The specific objective of this study was to determine whether the EAAs are released from primary afferents. Dorsal root ganglia (DRG) from 2 to 18-day-old rats dissected and cultured for 1-2 weeks were washed in modified Ringers recording solution for a period of 1 h to allow equilibration. The mean +/- S.E.M. baseline concentrations of EAAs recovered during a 5 min interval were 533.29 +/- 65.59 nmol for L-Glu and 106.67 +/- 14.05 nmol for L-Asp. Stimulation of DRG organotypic cultures with potassium resulted in a significant concentration-dependent increase in the release of both EAAs. The concentration of Asp increased to 166 +/- 17% and 203 +/- 13% in response to 5 min exposure of the culture to 25 and 50 mM potassium, respectively. The concentration of Glu increased to 155 +/- 12% and 226 +/- 18% of control in response to the same stimuli. In response to application of 50 mM potassium for 25 min, peak concentrations increased to 465 +/- 53% for Asp and 312 +/- 51% for Glu of the basal concentration. Exposure of the cultures to 1 or 10 microM capsaicin also caused release of both EAAs. The concentrations of Asp and Glu significantly increased to 204 +/- 11% and 165 +/- 15% of basal concentrations, respectively, in response to a 5 min exposure to 1 microM capsaicin. High [K+]e failed to increase the release of EAAs from cultures where DRG cell bodies were removed 72 h prior to release experiments. These results confirm results demonstrating release of EAA from mammalian spinal cord tissues and directly demonstrate for the first time that primary afferent fibers are specifically involved in this release.
多条证据表明，兴奋性氨基酸（EAA）（L-天冬氨酸（L-Asp）和L-谷氨酸（L-Glu））是脊髓中的兴奋性递质。本研究的具体目的是确定EAA是否从初级传入神经释放。将2至18日龄大鼠的背根神经节（DRG）解剖并培养1至2周，然后在改良的林格氏记录溶液中冲洗1小时以使其平衡。在5分钟间隔内回收的EAA的平均±标准误基线浓度，L-Glu为533.29±65.59 nmol，L-Asp为106.67±14.05 nmol。用钾刺激DRG器官型培养物导致两种EAA的释放均显著呈浓度依赖性增加。在培养物分别暴露于25和50 mM钾5分钟后，Asp的浓度分别增加到166±17%和203±13%。在相同刺激下，Glu的浓度增加到对照的155±12%和226±18%。在应用50 mM钾25分钟后，Asp的峰值浓度增加到基础浓度的465±53%，Glu增加到312±51%。将培养物暴露于1或10 μM辣椒素也会导致两种EAA的释放。在暴露于1 μM辣椒素5分钟后，Asp和Glu的浓度分别显著增加到基础浓度的204±11%和165±15%。高[K+]e未能增加在释放实验前72小时去除DRG细胞体的培养物中EAA的释放。这些结果证实了从哺乳动物脊髓组织中释放EAA的结果，并首次直接证明初级传入纤维特别参与了这种释放。
