Sakuma M, Yoshioka K, Suzuki H, Yanagisawa M, Onishi Y, Kobayashi N, Otsuka M
Department of Pharmacology, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Neuroscience. 1991;45(2):323-30. doi: 10.1016/0306-4522(91)90229-h.
Isolated spinal cords of newborn rats were perfused with artificial cerebrospinal fluid and the effects of substance P and its analogs on the release of endogenous GABA were examined. Application of substance P evoked a dose-dependent release of GABA from spinal cords. The threshold concentration of substance P for induction of a significant increase in the GABA release was 3 microM. The substance P-evoked GABA release was neither blocked by removal of Ca2+ from perfusion medium nor by tetrodotoxin. In contrast, the GABA release evoked by high K+ (90 mM) was abolished in Ca(2+)-free medium, and the GABA release evoked by veratridine (5 microM) was suppressed by tetrodotoxin (1 microM). A GABA uptake inhibitor, cis-4-hydroxynipecotic acid, markedly augmented the GABA release induced by high K+, but not that induced by substance P or veratridine. These results suggest the possibility that a carrier-mediated mechanism might be involved in the GABA release induced by substance P, as well as by veratridine, in the newborn rat spinal cord. Two N-terminal fragments of substance P, substance P free acid and substance P1-10 amide, as well as [D-Arg1,D-Trp7,9,Leu11]substance P (spantide), evoked an increase in the GABA release, whereas substance P1-6, and a C-terminal fragment, substance P5-11 were inactive. Somatostatin and compound 48/80 also evoked a GABA release, which was independent of external Ca2+ and resistant to tetrodotoxin. [D-Pro4,D-Trp7,9,10]substance P4-11 (10-15 microM) inhibited the GABA release evoked by substance P, somatostatin and compound 48/80.(ABSTRACT TRUNCATED AT 250 WORDS)
用人工脑脊液灌注新生大鼠的离体脊髓，研究P物质及其类似物对内源性γ-氨基丁酸（GABA）释放的影响。应用P物质可引起脊髓中GABA呈剂量依赖性释放。诱导GABA释放显著增加的P物质阈值浓度为3微摩尔。P物质引起的GABA释放既不被从灌注培养基中去除Ca2+所阻断，也不被河豚毒素阻断。相比之下，高钾（90毫摩尔）引起的GABA释放在无钙培养基中被消除，藜芦碱（5微摩尔）引起的GABA释放被河豚毒素（1微摩尔）抑制。一种GABA摄取抑制剂顺式-4-羟基尼克酸显著增强高钾诱导的GABA释放，但不增强P物质或藜芦碱诱导的GABA释放。这些结果提示，在新生大鼠脊髓中，载体介导机制可能参与P物质以及藜芦碱诱导的GABA释放。P物质的两个N端片段、P物质游离酸和P物质1-10酰胺，以及[D-Arg1，D-Trp7,9,Leu11]P物质（spantide）均可引起GABA释放增加，而P物质1-6和一个C端片段P物质5-11无活性。生长抑素和化合物48/80也可引起GABA释放，其释放与细胞外Ca2+无关且对河豚毒素有抗性。[D-Pro4，D-Trp7,9,10]P物质4-11（10-15微摩尔）抑制P物质、生长抑素和化合物48/80引起的GABA释放。（摘要截短于250字）
