Yamanaka K, Kitamura K, Kuriyama H
Pflugers Arch. 1987 Jan;408(1):10-7. doi: 10.1007/BF00581834.
Effects of neurotensin (NT) on the electrical and mechanical activities of longitudinal and circular muscles of the guinea-pig ileum were investigated using the microelectrode and isometric tension recording methods. In longitudinal muscles, the resting membrane potential was not affected by NT (0.1-30 nmol/l), but NT did provoke the contraction when applied in concentrations over 1 nmol/l. TTX (0.1 mumol/l) neither modified the resting membrane potential nor the contraction evoked by NT, under condition of pretreatment with alpha- and beta-adrenoceptor blockers. In circular muscles, NT (over 0.1 nmol/l) consistently hyperpolarized the membrane and increased the ionic conductance. The hyperpolarization appeared with a transient hyperpolarization, which gradually declined with a long time course. Using apamin and various concentrations of Ca, the NT-induced hyperpolarization was classified into two subtypes; fast and slow. The former was composed of maximum hyperpolarization due to activations of the Ca independent K channel, and the latter was composed of late hyperpolarization, due to activations of the Ca dependent K channel. During the NT-induced hyperpolarization in circular muscles, the amplitude of non-adrenergic, non-cholinergic inhibitory junction potential (i.j.p.) evoked by field stimulation was reduced. This reduction induced by 0.5 nmol/l NT was mainly due to hyperpolarization of the membrane, and that observed in a high concentration of NT (3 nmol/l) was directly involved in ionic mechanisms contributing to the generation of i.j.p. In circular muscles, NT (over 3 nmol/l) did relax the tissue pre-contracted with 17.8 mmol/l K, but NT (below 30 nmol/l) did not relax the tissue pre-contracted by 39.6 mmol/l K.(ABSTRACT TRUNCATED AT 250 WORDS)
采用微电极和等长张力记录法，研究了神经降压素（NT）对豚鼠回肠纵行肌和环行肌电活动及机械活动的影响。在纵行肌中，NT（0.1 - 30 nmol/L）不影响静息膜电位，但浓度超过1 nmol/L时可引起收缩。在α和β肾上腺素能受体阻滞剂预处理的条件下，TTX（0.1 μmol/L）既不改变静息膜电位，也不改变NT引起的收缩。在环行肌中，NT（超过0.1 nmol/L）持续使膜超极化并增加离子电导。超极化表现为短暂的超极化，随后随时间逐渐下降。使用蜂毒明肽和不同浓度的钙，将NT诱导的超极化分为两种亚型：快速型和缓慢型。前者由钙依赖性钾通道激活导致的最大超极化组成，后者由钙依赖性钾通道激活导致的后期超极化组成。在环行肌中NT诱导超极化期间，场刺激诱发的非肾上腺素能、非胆碱能抑制性接头电位（i.j.p.）的幅度降低。0.5 nmol/L NT引起的这种降低主要是由于膜超极化，而在高浓度NT（3 nmol/L）时观察到的降低直接涉及到i.j.p.产生的离子机制。在环行肌中，NT（超过3 nmol/L）可使预先用17.8 mmol/L钾预收缩的组织松弛，但NT（低于30 nmol/L）不能使预先用39.6 mmol/L钾预收缩的组织松弛。（摘要截于250字）
