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Orexin A affects ascending contraction depending on downstream cholinergic neurons and descending relaxation through

Yuji Satoh1, Yutaka Okishio, Yasu-Taka Azuma

  • 1Department of Veterinary Pharmacology, Graduate school of Life and Environmental Sciences, Osaka Prefecture University, Gakuen-cho 1-1, Sakai 599-9531, Japan.

Neuropharmacology
|June 10, 2006
PubMed

Insights

Orexin A (OXA) significantly influences mouse jejunal peristalsis by modulating ascending contractions and descending relaxation. Blocking orexin-1 receptors impacts these neural reflexes, highlighting OXA

Area of Science:

  • Gastroenterology
  • Neuroscience
  • Pharmacology

Background:

  • Peristalsis, the wave-like muscle contractions that move food through the digestive tract, is regulated by complex neural pathways.
  • Orexin, a neuropeptide, is known for its role in regulating sleep-wake cycles and appetite, but its involvement in gastrointestinal motility is less understood.

Purpose of the Study:

  • To investigate the role of orexin in the neural control of peristalsis in mouse jejunal segments.
  • To determine the specific neural pathways and receptors involved in orexin-mediated effects on jejunal motility.

Main Methods:

  • Mouse jejunal segments were subjected to localized distension to induce peristaltic reflexes.
  • Pharmacological agents including atropine, tetrodotoxin, hexamethonium, l-nitroarginine, orexin A (OXA), and the orexin-1 receptor antagonist SB-334867-A were used to probe neural pathways.
  • Desensitization and exogenous administration of OXA and nicotine were employed to assess their effects on ascending contraction and descending relaxation.

Main Results:

  • Ascending contraction was mediated by cholinergic and intrinsic enteric neurons, and significantly inhibited by orexin-1 receptor antagonism and hexamethonium.
  • Descending relaxation involved nitrergic pathways and was partially inhibited by orexin-1 receptor antagonism and hexamethonium.
  • Exogenous OXA induced contraction and relaxation, with distinct receptor-mediated pathways compared to nicotine.

Conclusions:

  • Orexin A plays a significant role in both ascending and descending neural reflexes governing peristalsis in the mouse jejunum.
  • Orexin signaling, particularly through the orexin-1 receptor, is a key component of the enteric nervous system's control over gastrointestinal motility.

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