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Effect of alpha-2 adrenoceptor antagonists on colonic function in rats

O Yamamoto1, H Niida, K Tajima

  • 1Discovery Research Laboratories, Nippon Shinyaku Co. Ltd., Nishiohji-Hachijo, Minami-ku, Kyoto, Japan. o.yamamoto@po.nippon-shinyaku.co.jp

Neurogastroenterology and Motility
|June 27, 2000
PubMed

Insights

Alpha-2 adrenoceptor antagonists specifically reduce stress-induced colonic motor function in rats. These antagonists, like yohimbine and idazoxan, show targeted effects on stress-related fecal excretion, unlike other tested agents.

Area of Science:

  • Pharmacology
  • Gastroenterology
  • Neuroscience

Background:

  • Colonic function is modulated by various neurotransmitters and stress.
  • Alpha-2 adrenoceptors play a role in regulating gastrointestinal motility.
  • Understanding the specific mechanisms of stress-induced colonic dysfunction is crucial for developing targeted therapies.

Purpose of the Study:

  • To investigate the effects of alpha-2 adrenoceptor antagonists on stress-induced colonic function.
  • To compare the efficacy of alpha-2 adrenoceptor antagonists with other agents like atropine and ondansetron in modulating colonic responses.
  • To determine the specificity of alpha-2 adrenoceptor antagonists in inhibiting stress-related colonic motor activity.

Main Methods:

  • Administration of alpha-2 adrenoceptor antagonists (yohimbine, idazoxan) and control drugs (atropine, ondansetron) to rats.
  • Stimulation of colonic function using water-avoidance stress, 5-hydroxytryptamine (5-HT), bethanechol, and castor oil.
  • Measurement of faecal excretion and incidence of diarrhoea as indicators of colonic motor function.

Main Results:

  • Yohimbine, idazoxan, and atropine significantly inhibited water-avoidance stress-stimulated faecal excretion; ondansetron did not.
  • Alpha-2 antagonists did not inhibit 5-HT- or bethanechol-stimulated faecal excretion, whereas atropine did.
  • Idazoxan, but not yohimbine, significantly inhibited castor oil-induced diarrhoea, while atropine and ondansetron inhibited diarrhoea over a 2-h period.

Conclusions:

  • Alpha-2 adrenoceptor antagonists selectively inhibit stress-induced colonic motor function in rats.
  • These findings highlight the specific role of alpha-2 adrenoceptors in mediating the colonic response to stress.
  • Alpha-2 adrenoceptor antagonists represent a potential therapeutic target for stress-related gastrointestinal disorders.

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