Lundy P M, Hamilton M G, Frew R
Pharmacology and Therapeutics, Defence Research Establishment Suffield, Alberta, Canada.
Brain Res. 1994 Apr 18;643(1-2):204-10. doi: 10.1016/0006-8993(94)90026-4.
Ca2+ influx was measured in rat and chicken brain synaptosomes in the presence of a number of pharmacological tools which have recently been used to define voltage-sensitive Ca(2+)-channel (VSCC) types. In chicken brain synaptosomes. VSCCs which, because of their sensitivity to inhibition by omega-conotoxin (omega-CgTx), are thought to be exclusively N-type, the P-type VSCC polyamine inhibitor FTX (from Agelenopsis aperta venom; 1 microliters/ml), its synthetic analogue, sFTX (1-5 mM) and the polypeptides AgaIVA (IC50 0.29 microM) and omega-CgTx MVIIC (IC50 0.0022 microM) inhibited 70-100% of the measurable K+ stimulated Ca2+ influx. The prototypical N-channel VSCC inhibitor omega-CgTx GVIA (IC50 0.014 microM), Cd2+ (50 microM) and diluted venom from Hololena curta (1:2,500) also caused complete or almost complete, inhibition of Ca2+ influx. In comparable studies using rat brain synaptosomes, sFTX (1-10 mM) caused a dose-dependent reduction of Ca2+ influx, while FTX (1 microliters/ml) and AgaIVA (IC50 0.02 microM) completely inhibited Ca2+ influx. Similar to the findings in chicken synaptosomes, Cd2+ (50 microM) and H. curta (1:2,500 dilution) both inhibited K+ stimulated influx by > 80% whereas omega-CgTx (1 microM) only caused a maximum 25% inhibition. Both sFTX and its congener spermine, inhibited [125I]omega-CgTx binding to rat and chicken synaptosomal membranes. These results strongly implicate P-type channels as the major VSCC in rat brain. The results also clearly demonstrate a heretofore unrecognized, novel, FTX/AgaIVA/omega-CgTx GVIA/omega-CgTx MVIIC-sensitive VSCC in chicken brain.
在存在多种药理学工具的情况下，对大鼠和鸡脑突触体中的Ca2+内流进行了测量，这些药理学工具最近已被用于定义电压敏感性Ca(2+)通道（VSCC）类型。在鸡脑突触体中，由于对ω-芋螺毒素（ω-CgTx）抑制敏感而被认为是唯一N型的VSCC、P型VSCC多胺抑制剂FTX（来自墨西哥毒蛛毒液；1微升/毫升）、其合成类似物sFTX（1-5毫摩尔）以及多肽AgaIVA（IC50 0.29微摩尔）和ω-CgTx MVIIC（IC50 0.0022微摩尔）抑制了70-100%的可测量的K+刺激的Ca2+内流。典型的N通道VSCC抑制剂ω-CgTx GVIA（IC50 0.014微摩尔）、Cd2+（50微摩尔）和来自短孔蛛的稀释毒液（1:2500）也导致Ca(2+)内流完全或几乎完全受到抑制。在使用大鼠脑突触体的类似研究中，sFTX（1-10毫摩尔）导致Ca2+内流呈剂量依赖性减少，而FTX（1微升/毫升）和AgaIVA（IC50 0.02微摩尔）完全抑制了Ca2+内流。与鸡突触体中的发现相似，Cd2+（50微摩尔）和短孔蛛（1:2500稀释）均抑制K+刺激的内流超过80%，而ω-CgTx（1微摩尔）仅引起最大25%的抑制。sFTX及其同系物精胺均抑制[125I]ω-CgTx与大鼠和鸡突触体膜的结合。这些结果强烈表明P型通道是大鼠脑中主要的VSCC。结果还清楚地证明了鸡脑中一种迄今未被认识的新型FTX/AgaIVA/ω-CgTx GVIA/ω-CgTx MVIIC敏感的VSCC。
