Shimuta S I, Nouailhetas V L, Valero V B, Paiva A C, Paiva T B
Pflugers Arch. 1982 Aug;394(2):186-90. doi: 10.1007/BF00582923.
The possibility that the guinea-pig ileum's contractile response to K+-rich solutions is partly mediated by acetylcholine release from the intramural nervous tissue was examined by studying the inhibition of that response by atropine at different values of [Na+]o. In a medium in which the NaCl was replaced by iso-osmotic glucose, the response to high [K+]o was not greatly affected, while the responses to acetylcholine and to other agonists were significantly reduced. In control medium (149 mM Na+), atropine (10(-7) M) partly inhibited the responses to K+-rich solutions and to agonists such as histamine, 5-hydroxytryptamine and bradykinin. When [Na+]o was reduced to 12 mM, by iso-osmotic substitution of glucose for NaCl, the response to high K+ was no longer inhibited by atropine, which still partly inhibited the contractions elicited by the three agonists and totally blocked the response of acetylcholine. It is proposed that atropine's inhibition of the response to high K+ and to agonists is not due to its specific anti-muscarinic effect, but to an unspecific action, which in the case of the agonists is independent of [Na+]o. In addition, the inhibition of the response to high K+ would results from a different Na+-dependent mechanisms, possibly involving the stimulation of the Na-K pump by atropine. This is supported by the observation that this drug partly relaxed ileum preparations that were contracted by ouabain.
通过研究在不同的细胞外钠离子浓度（[Na⁺]o）下阿托品对豚鼠回肠对富含钾离子溶液的收缩反应的抑制作用，来检验壁内神经组织释放乙酰胆碱是否部分介导了豚鼠回肠对富含钾离子溶液的收缩反应。在一种用等渗葡萄糖替代氯化钠的培养基中，对高细胞外钾离子浓度（[K⁺]o）的反应没有受到很大影响，而对乙酰胆碱和其他激动剂的反应则显著降低。在对照培养基（149 mM Na⁺）中，阿托品（10⁻⁷ M）部分抑制了对富含钾离子溶液以及对组胺、5-羟色胺和缓激肽等激动剂的反应。当通过用葡萄糖等渗替代氯化钠使细胞外钠离子浓度（[Na⁺]o）降至12 mM时，对高钾离子的反应不再被阿托品抑制，而阿托品仍部分抑制由这三种激动剂引起的收缩，并完全阻断乙酰胆碱的反应。有人提出，阿托品对高钾离子和激动剂反应的抑制并非因其特异性抗毒蕈碱作用，而是由于一种非特异性作用，就激动剂而言，这种作用与细胞外钠离子浓度（[Na⁺]o）无关。此外，对高钾离子反应的抑制可能源于一种不同的钠离子依赖性机制，可能涉及阿托品对钠钾泵的刺激。哇巴因使回肠制剂收缩后，这种药物能使其部分松弛，这一观察结果支持了这一点。
