Behar J, Guenard V, Walsh J H, Biancani P
Department of Medicine, Rhode Island Hospital, Providence.
Am J Physiol. 1989 Sep;257(3 Pt 1):G380-5. doi: 10.1152/ajpgi.1989.257.3.G380.
Vasoactive intestinal polypeptide (VIP) and acetylcholine were evaluated as possible inhibitory and excitatory neurotransmitters in the cat esophageal circular smooth muscle. Circular muscle strips 2 mm in thickness were obtained from 1 to 3.4 cm above the lower esophageal sphincter and tested in vitro. Muscle strips contracted with bethanechol (10(-5) M) were relaxed by electrical stimulation (0.5-5 Hz) and by VIP (10(-8)-10(-6) M). Relaxation induced by electrical stimulation was blocked by tetrodotoxin, whereas VIP-induced relaxation was not affected. Highly specific VIP antiserum (5%) antagonized both VIP and electrically induced relaxation, and the antagonism was eliminated when the antiserum was neutralized with VIP (10(-6.5) M). Dopamine (10(-4) M) reduced the relaxation induced both by exogenous VIP and by electrical stimulation but did not affect the relaxation caused by sodium nitroprusside (10(-8)-10(-5) M). In untreated strips, physostigmine (10(-10)-10(-8) M) enhanced the off contraction in response to electrical stimulation, whereas atropine caused a dose-dependent reduction with complete abolition at 10(-4) M. These data suggest that in the esophagus inhibition and excitation are mediated by distinct mechanisms: VIP mediates inhibition and acetylcholine is responsible for the off contraction in response to electrical stimulation.
血管活性肠肽（VIP）和乙酰胆碱被评估为猫食管环形平滑肌中可能的抑制性和兴奋性神经递质。从食管下括约肌上方1至3.4厘米处获取厚度为2毫米的环形肌条，并进行体外测试。用氨甲酰甲胆碱（10⁻⁵ M）收缩的肌条可通过电刺激（0.5 - 5 Hz）和VIP（10⁻⁸ - 10⁻⁶ M）松弛。电刺激诱导的松弛被河豚毒素阻断，而VIP诱导的松弛不受影响。高特异性VIP抗血清（5%）拮抗VIP和电诱导的松弛，当抗血清用VIP（10⁻⁶.⁵ M）中和时，拮抗作用消除。多巴胺（10⁻⁴ M）减少外源性VIP和电刺激诱导的松弛，但不影响硝普钠（10⁻⁸ - 10⁻⁵ M）引起的松弛。在未处理的肌条中，毒扁豆碱（10⁻¹⁰ - 10⁻⁸ M）增强电刺激后的舒张后收缩，而阿托品引起剂量依赖性降低，在10⁻⁴ M时完全消除。这些数据表明，在食管中，抑制和兴奋由不同机制介导：VIP介导抑制，乙酰胆碱负责电刺激后的舒张后收缩。
