Charactrristics of motilin-induced contraction and its developmental change in the chicken gastrointestinal tract

鸡胃动素(ch-MT)通过肌源性和神经源性(主要是胆碱能)机制引起鸡胃(腺胃)纵行肌条的收缩。另一方面，ch-MT仅通过肌源性机制收缩小肠。胃肠道对ch-MT的敏感性具有区域依赖性(空肠、回肠、十二指肠、腺胃、结肠)。在体内，CH-MT对胃运动有刺激作用。本实验旨在研究对ch-MT的反应性和电场刺激(EFS)诱导的反应特征的发育变化，以及NO和ch-MT之间的相互作用。免疫组织化学研究还检测了含ch-MT的细胞的存在。Ch-MT诱发收缩的发展：由于…间接收缩的减少，ch-MT诱导的收缩的幅度随孵化天数(1-50天)的增加而逐渐降低更多的高胆碱能神经。但对Ach和5-羟色胺的反应以及ch-MT引起的回肠收缩在每个孵化日均无变化。这些结果提示MT在鸡小肠运动、ch-MT和NO相互作用中的生理作用：L-甲基硝基精氨酸(L-NAME)增强和L-精氨酸抑制ch-MT和EFS引起的PROV收缩，而不影响对Ach和5-HT的反应。然而，在回肠和阿托品处理的Prov，L和L精氨酸都不能改变对ch-MT的反应。NO合酶抑制通过减轻内源性NO介导的突触前抑制对神经ACh释放的抑制，增强了PROV内ch-MT和EFS的收缩反应。然而，抑制一氧化氮合酶并不改变ch-MT在胃肠平滑肌上的生肌(直接)作用。鸡PROV的神经支配：PROV共支配5种自主神经：胆碱能兴奋神经(0.1~20 Hz)、非肾上腺素能非胆碱能(NANC)兴奋神经(0.5~1 Hz和10 Hz以上)、无抑制神经(2~7 Hz)、NANC和非NO抑制神经(7 Hz以上)。孵化后1d，胆碱能神经和NO神经支配已基本完成，而NANC、Non-NO抑制神经支配较慢。免疫组织化学：用兔制备特异性ch-MT抗体。MT免疫反应阳性细胞见于幽门、十二指肠、空肠、回肠，而在胃、胃、直肠和盲肠中未见。与其他区域相比，含细胞存在区的MT对ch-MT的敏感性更高。MT是鸡肠道中的一种运动刺激激素。较少

Chicken motilin (ch-MT) caused contractions of longitudinal muscle strips of the chicken stomach (proventriculus, Prov) though both myogenic and neurogenic (mostly cholinergic) mechanisms. On the other hand, ch-MT contracted the small intestine through only a myogenic mechanism. The sensitivity of gastrointestinal tracts to ch-MT was region-dependent (jejunum > ileum > duodenum > proventricculus > colon). Ch-MT also stimulated the gastric motility in vivo. The present experiments were designed to investigate developmental changes in responsiveness to ch-MT and in characteristics of electrical field stimulation (EFS)-induced responses, and interaction between NO and ch-MT. Immunohistochemical study was also carried out to examine the presence of ch-MT containing cells. Development of ch-MT-induced contraction : Amplitude of the ch-MT-induced contraction not-log EC_<50> value decreased gradually depending on hatching days(1-50 days), because of the reduction of indirect contraction throu … More gh cholinergic nerves. But response to a Ach and 5-HT in Prov, and ch-MT-induced contraction in the ileum were not changed at every hatching day. These result suggest the physiological roles of MT in the chicken small intestinal motility ch-MT and NO interaction : L-Nitroarginine methyleaster (L-NAME) potentiated and L-arginine inhibited ch-MT and EFS-induced contractions in Prov without affecting the response to Ach and 5-HT. However, in the ileum and atropine-treated Prov, neither L-NAME nor L-arginine modified the responses to ch-MT. NO synthase inhibition potentiated the contractile response of ch-MT and EFS in Prov through reduction of endogenous NO-mediated presynaptic inhibition on neural ACh release. However, NOS inhibition did nor modify the myogenic (direct) action of ch-MT in gastric and intestinal smooth muscles. Innervation of chicken Prov : Prov was innervated 5 types of autonomic nerves, such as cholinergic excitatory nerve (0.1 - 20 Hz), nonadrenergicnoncholinergic (NANC) excitatory nerves (0.5 - 1 Hz and over 10Hz), NO inhibitory nerve (2 - 7 Hz), NANC, nonNO inhibitory nerve (over 7 Hz). Cholinergic and NO innervation was already completed on 1 day after hatching but NANC, nonNO inhibitory nerve was slowly. Immunohisyochemistry : Specific ch-MT antibody was produced using rabbits. MT-immunoreactive cells were present in the pylorus, duodenum, jejunum, ileum but not in the gizzard, Prov, rectum and caecum. MT containing cell present regions had a high sensitivity to ch-MT compared with other regions. MT is a motor stimulating hormone in the chicken intestinal tracts. Less