大鼠骶髓后连合核神经元兴奋性氨基酸诱导的反应

EXCITATORY AMINO ACID-INDUCED RESPONSES IN RAT SACRAL DORSAL COMMISSURAL NEURONS

应用制霉菌素穿孔全细胞电压钳技术，研究急性分离的大鼠骶髓后连合核（ＳＤＣＮ）神经元对谷氨酸受体激动剂的反应。钳制电压为－４０ｍＶ的条件下，Ｌ－谷氨酸（Ｇｌｕ），Ｎ－甲基－Ｄ－门冬氨酸（ＮＭＤＡ），使君子酸（ＱＡ），α－氨基－３－羟基－５－甲基异倾阶－４－丙酸（ＡＭＰＡ）和红藻氨酸（ＫＡ）均诱导产生内向电流。随着激动剂浓度的增高，这些电流的量效关系曲线呈典型的Ｓ型。ＥＣ５０值分别是Ｇｌｕ３．３×１０－５Ｍ，ＮＭＤＡ９．０×１０－ＳＭ，ＱＡ６．４×１０７Ｍ，ＡＭＰＡ１．３×１０－４及ＫＡｇ．６×ｕ１０－５Ｍ。Ｎｉｌｌ系数分别是Ｇｌｕ０．７４，ＮＭＤＡ０．８３，ＱＡ１．３，ＡＭＰＡ１．１和ＫＡ１．３。代谢型谷氨酸受体激动剂ｔＡＣＰＤ（１０－３Ｍ）未能诱导出电流．Ｃｙｃｌｏｔｈｉａｚｉｄｅ显著增强ＫＡ和ＡＭＰＡ诱导的反应。相反，伴刀豆球蛋白Ａ（ＣｏｎＡ）对ＫＡ和ＡＭＰＡ反应作用甚微，提示ＳＤＣＮ神经元主要表达ＡＭＰＡ型非ＮＭＤＡ受体。

The responses to GluR agonists were studied in neurons acutely dissociated from rat sacral dorsalcommissural nucleus (SDCN) using nystatin perforated whole-cell patch recording configuration under voltageclamp condition. At a holding potential of -40 mV, L-glutamate (Gin ), N-methyl-D-aspartate (NMDA).quisqualate (QA), α-amino- 3 -hydroxy- 5-methyl- 4-isoxazol e prop ic nic acid (AM PA ) and kainate (KA ) evoked inward currents. The currents increased in a sigmoidal fashion with increasing agonist concentrations. The half-maximum concentration (EC50) values were 3. 3 × 10-5M for Glu, 9. 0 × 10-5M for NMDA, 6. 4 × 10-7M foe QA, 1. 3 ×10-4M for AMPA and 9. 6 × 10-5M for KA. The Hill coefficients of Gin-, NMDA-, QA-, AMPA- and KA-inducedresponses were 0. 74, 0. 83, 1. 3, 1. 1 and 1. 3, respectively. trans-1-amino-cyclopentane-1, 3-dicarboxylate(tACPD), which is a selective mGluR agonist, evoked no response at concentration up to 10-3M. Cyclothiazidestrongly potentiated both KA- and AMPA-induced responses. In contrast, ConA had only a weak effect on bothKA- and AMPA-induced responses, suggesting that the dominant non-NMDA receptors expressed in the SDCNneurons are AMPA receptors.