- 作者: 邱麗珠; 張傳?
- 作者服務機構: 國立臺灣大學醫學院藥理學科
- 中文摘要:
本實驗以小白鼠膈神經-橫胴膜和小雞二頸肌標本,研究clonidine對神經-肌傳遞系統的影響。我們發現clonidine
不影響直接刺激肌肉與KCl引起的收縮反應,?會抑制間接刺激反應;其作用隨濃度之增而增且具可逆性,可被diami-
nopyridine對抗,但yohimbine,phentolamine或physostigmine則不能對抗。終板電位和微小終板電位大小均被降低
,但其量子數不受影響。此外,clonidine亦降低去神經膈膜的ACh反應與其濃度-反應曲線斜率,以及小雞二頸肌之
carbachol反應,但對小雞之ACh反應大小不影響,因clonidine可抑制乙醯膽胺脂?活性。然而clonidine在二種肌肉均
會加速ACh反應之衰減。因此,我們結論:clonidine抑制神經-肌傳遞,是經由非競爭性地阻斷ACh感受體,可能是作
用於ACh管道而不是在感受體的識別區;而其抑制神經-肌傳遞作用並非經由阻斷α -adrenoceptor而來,顯示運動神
經末梢並無 α -adrenoceptor存在。
或 - 英文摘要: The effects of clonidine on neuromuscular transmission were investigated in the mouse phrenicnerve-diaphragms and chicken biventer cervicis. Clonidine inhibited the indirect twitch response dose-dependentiy and reversibly without an effeot on the direct response of the muscles to electrical stimulationand KCI. This effect was antagonized effectively by diaminopyridine but not by yohimbine, phentolamineor physostigmine. The quantal content was not affected although the amplitudes of end-plate potential(epp) and spontaneous miniature epp (mepp) were markedly depressed. Clonidine also decreased the slopeof the ACh dose-response curve and maximal response in denervated mouse diaphragms as well as thecarbachol response in the chinck muscle. In the latter, ACh response was not depressed by clonidineprobably because of its inherent anticholinesterase activity. Clonidine facilitated the fading of ACh-contracture either in mouse or chick muscle. It is concluded that clonidine impairs the neuromusculartransmission by a noncompetitive blockade of ACh receptors, most likely affecting the ACh channel butnot the recognition site of the ACh receptor. Its inhibitory effect is not mediated by α -adrenoceptor,suggesting that there is no α -adrenoceptor on the motor nerve terminal to modulate the transmitterrelease.
- 中文關鍵字: clonidine; neuromuscular transmission; acetylcholine receptor
- 英文關鍵字: --