Snape W J, Hyman P E, Mayer E A, Sevy N, Kao H W, Root D
Gastroenterology. 1987 Oct;93(4):823-8. doi: 10.1016/0016-5085(87)90446-x.
The effect of neurotensin on smooth muscle contraction was compared in strips from rabbit proximal and distal circular colonic muscle. The effective dose for neurotensin stimulation that caused a 50% response in both tissues was similar (1.3 X 10(-10) M). The maximal isometric stress, however, was greater in the distal colon than in the proximal colon (p less than 0.01). Neurotensin stimulation of both proximal and distal colon was unaffected by tetrodotoxin, phentolamine, propranolol, naloxone, or atropine. Neurotensin-stimulated contraction was inhibited by "Ca2+-free" (pCa = 5.1) or La3+ buffer. Verapamil (10(-6) M) or nitroprusside (10(-4) M) decreased neurotensin stimulation of proximal and distal colon by approximately 40% (p less than 0.05). Removal of Ca2+ from the buffer inhibited stimulation of muscle contraction by high extracellular potassium [( K+]o) more than bethanechol stimulation (p less than 0.01). La3+ (1 mM) inhibited the contraction stimulated by bethanechol or increased [K+]o. Although verapamil inhibited contraction by bethanechol and increased [K+]o by approximately 50%, nitroprusside had no effect on the contraction mediated by these stimulants. 8-Bromo-guanosine 3',5'-cyclic monophosphate (cGMP) inhibited neurotensin, but not [K+]o or bethanechol-stimulated contraction. These data suggest (a) neurotensin stimulated colonic contractions at a concentration that is potentially physiologic, (b) neurotensin stimulated colonic smooth muscle directly without neural mediation, (c) neurotensin stimulation of colonic muscle is controlled by [Ca2+]o and [cGMP]i.
在兔近端和远端结肠环行肌条中比较了神经降压素对平滑肌收缩的作用。在两种组织中引起50%反应的神经降压素刺激有效剂量相似（1.3×10⁻¹⁰ M）。然而，远端结肠的最大等长张力大于近端结肠（p<0.01）。神经降压素对近端和远端结肠的刺激不受河豚毒素、酚妥拉明、普萘洛尔、纳洛酮或阿托品的影响。神经降压素刺激的收缩被“无钙”（pCa = 5.1）或La³⁺缓冲液抑制。维拉帕米（10⁻⁶ M）或硝普钠（10⁻⁴ M）使神经降压素对近端和远端结肠的刺激降低约40%（p<0.05）。从缓冲液中去除Ca²⁺对高细胞外钾（[K⁺]o）刺激的肌肉收缩的抑制作用大于氨甲酰甲胆碱刺激（p<0.01）。La³⁺（1 mM）抑制氨甲酰甲胆碱刺激或[K⁺]o增加引起的收缩。尽管维拉帕米抑制氨甲酰甲胆碱引起的收缩并使[K⁺]o增加约50%，但硝普钠对这些刺激物介导的收缩无影响。8-溴鸟苷3',5'-环磷酸（cGMP）抑制神经降压素刺激的收缩，但不抑制[K⁺]o或氨甲酰甲胆碱刺激的收缩。这些数据表明：（a）神经降压素以潜在生理浓度刺激结肠收缩；（b）神经降压素直接刺激结肠平滑肌，无神经介导；（c）神经降压素对结肠肌肉的刺激受细胞外钙（[Ca²⁺]o）和细胞内cGMP（[cGMP]i）控制。
