| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
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
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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
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