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）机制引起鸡胃纵肌条（proveniculus, provv）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的敏感性是区域依赖性的（空肠b>回肠>十二指肠>前脑室>结肠）。Ch-MT在体内也能刺激胃运动。本实验旨在探讨NO与ch-MT的相互作用，以及NO对ch-MT的反应性、电场刺激（EFS）诱发的反应特征的发育变化。同时采用免疫组化方法检测含ch-MT细胞的存在。ch- mt诱导收缩的发展：ch- mt诱导收缩的振幅（非对数EC_<50>值）随着孵化天数（1-50天）的增加而逐渐降低，这是由于间接收缩通过胆碱能神经减少所致。但在每个孵化日，回肠对乙酰胆碱和5-羟色胺的反应以及ch- mt诱导的收缩并没有改变。上述结果提示MT在鸡小肠运动ch-MT与NO相互作用中的生理作用：l -硝基精氨酸甲酯（L-NAME）增强和抑制ch-MT和efs诱导的Prov收缩，但不影响对Ach和5-HT的反应。然而，在回肠和阿托品治疗的Prov中，L-NAME和l -精氨酸都没有改变ch-MT的反应。NO合成酶抑制通过减少内源性NO介导的突触前神经乙酰胆碱释放抑制，增强了ch-MT和EFS的收缩反应。然而，NOS抑制并未改变ch-MT在胃和肠平滑肌中的成肌（直接）作用。鸡Prov的神经支配：Prov可支配5种自主神经：胆碱能兴奋神经（0.1 ~ 20hz）、非肾上腺素能-非胆碱能兴奋神经（0.5 ~ 1hz及10Hz以上）、NO抑制神经（2 ~ 7hz）、NANC、非NO抑制神经（7hz以上）。胆碱能神经和一氧化氮神经的支配在孵化后1天已完成，而NANC和非一氧化氮抑制神经的支配则较慢。免疫组化：用家兔制备特异性ch-MT抗体。mt免疫反应细胞存在于幽门、十二指肠、空肠、回肠，但不存在于砂囊、脾脏、直肠和盲肠。与其他区域相比，含有细胞存在区的MT对ch-MT具有较高的敏感性。MT是鸡肠道中的一种运动刺激激素。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