Ryall R W
Ciba Found Symp. 1982(91):267-80. doi: 10.1002/9780470720738.ch15.
Substance P administered iontophoretically to Renshaw cells in the cat had a dual effect, sometimes causing excitation and at other times inhibiting the excitatory effect of acetylcholine (ACh). The inhibitory effect was selective for the nicotinic receptors on Renshaw cells and the excitatory effect seemed to be due to the release of ACh from cholinergic terminals. It has not been possible to demonstrate a similar inhibitory effect on nicotinic receptors at the neuromuscular junction in frogs or in the chick, although a small agonist effect was occasionally observed. In the atropinized cat, intra-arterial injections of ACh to the superior cervical ganglion cause both a rise in blood pressure and contractions of the nictitating membrane which are abolished by hexamethonium. Intra-arterial injections of substance P partially blocked these nicotinic actions of ACh, but no excitatory effect of substance P was observed. These observations are discussed in relation to other studies and indicate that the polypeptide could function as an inhibitory or facilitatory regulator of cholinergically mediated responses at some but not all cholinergic synapses.
以离子透入法将P物质施用于猫的闰绍细胞时，会产生双重效应，有时引起兴奋，有时则抑制乙酰胆碱（ACh）的兴奋作用。这种抑制作用对闰绍细胞上的烟碱样受体具有选择性，而兴奋作用似乎是由于胆碱能终末释放ACh所致。虽然偶尔观察到轻微的激动剂效应，但尚未证实在青蛙或鸡的神经肌肉接头处对烟碱样受体有类似的抑制作用。在阿托品化的猫中，向上颈神经节动脉内注射ACh会导致血压升高和瞬膜收缩，而六甲铵可消除这些反应。动脉内注射P物质可部分阻断ACh的这些烟碱样作用，但未观察到P物质的兴奋效应。结合其他研究对这些观察结果进行了讨论，结果表明该多肽在某些但并非所有胆碱能突触处可能作为胆碱能介导反应的抑制性或促进性调节因子发挥作用。
