Korczynski W, Ceregrzyn M, Kato I, Wolinski J, Zabielski R
Department of Gastrointestinal Physiology, The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Science, Jabłonna, Poland.
J Physiol Pharmacol. 2006 Nov;57 Suppl 6:43-54.
Orexin-A and -B (OXA, OXB) are peptides involved in many gastrointestinal (GI) functions, including motility. Orexins, their precursors and receptors are present in the GI tract. The expression of orexins increases in the hypothalamus and gastrointestinal tract in response to fasting. We have examined the effect of OXA and OXB on GI motility in vitro in fed and fasted rats. The intestinal segments were mounted in chambers filled with Krebs solution. Isotonic contractions were measured in response to acetylcholine (10(-5) M), electric field stimulation (EFS), and orexins (10(-9)-10(-7) M) alone or in the presence of orexin-1 type receptor antagonist, SB- 334867 (10(-5) M), tetrodotoxin (TTX) 10(-6) M, or atropine (10(-5) M). Orexins caused a dose-dependent increase of intestinal segment contractions with a more pronounced effect of OXB over OXA. Fasting did not influence orexin-induced responses. Incubation with SB-334867 led to a marked decrease in orexin-induced contractions in OXA-treated segments, while those of OXB were not affected. Atropine diminished contractions only in fasted animals, while TTX led to a decreased response to orexins in both groups. The results show that OXB is predominant in inducing gut motility response, that the effect of orexins is not fully dependent on cholinergic and Na(+) transmissions, and that involvement of other transmitters is possible.
食欲素A和食欲素B（OXA、OXB）是参与包括胃肠动力在内的多种胃肠（GI）功能的肽类。食欲素、其前体和受体存在于胃肠道中。禁食时，下丘脑和胃肠道中食欲素的表达会增加。我们研究了OXA和OXB对喂食和禁食大鼠离体胃肠动力的影响。将肠段安装在充满 Krebs 溶液的小室中。测量等张收缩对乙酰胆碱（10⁻⁵ M）、电场刺激（EFS）以及单独的食欲素（10⁻⁹ - 10⁻⁷ M）或在存在食欲素-1型受体拮抗剂SB-334867（10⁻⁵ M）、河豚毒素（TTX）10⁻⁶ M或阿托品（10⁻⁵ M）的情况下的反应。食欲素导致肠段收缩呈剂量依赖性增加，其中OXB的作用比OXA更明显。禁食不影响食欲素诱导的反应。与SB-334867孵育导致OXA处理的肠段中食欲素诱导的收缩明显减少，而OXB处理的肠段则不受影响。阿托品仅使禁食动物的收缩减弱，而TTX导致两组对食欲素的反应均降低。结果表明，OXB在诱导肠道动力反应中占主导地位，食欲素的作用并不完全依赖于胆碱能和Na⁺传递，并且可能涉及其他递质。
