Xylazine-induced delay of small intestinal transit in mice

Eur J Pharmacol. 1982 Sep 10;83(1-2):55-60. doi: 10.1016/0014-2999(82)90285-0.


Subcutaneous injection of xylazine (0.1-3.0 mg/kg) produced a dose-dependent delay of small intestinal transit without affecting gastric emptying in the conscious mice. The xylazine-induced delay of small intestinal transit was antagonized by alpha 2-adrenoceptor antagonists, e.g., yohimbine, piperoxan and tolazoline. The antagonism of xylazine activity by yohimbine was dose-dependent, and the maximal antagonistic effect was seen at 1 mg/kg. Other adrenoceptor antagonists with only alpha 1-blocking activity, e.g., thymoxamine, prazosin and phenoxybenzamine at the doses studied did not reduce the depressant effect of xylazine on small intestinal transit. A beta-adrenergic antagonist, propranolol was not effective in reducing xylazine activity. The opioid antagonist, naloxone did not reduce the effective of xylazine, nor did yohimbine antagonize the morphine-induced delay of small intestinal transit. The xylazine-induced delay of small intestinal transit was not altered by atropine, hexamethonium, haloperidol, methysergide, chlorpheniramine or cimetidine. Pretreatment of mice with reserpine and alpha-methyl-p-tyrosine or 6-hydroxydopamine failed to reduce the intestinal effect of xylazine. These results suggest that xylazine-induced delay of small intestinal transit is mediated by postjunctional alpha 2-adrenoceptors and appears not to involve activation of opioid, cholinergic, dopaminergic, histaminergic, or serotonergic receptors.

MeSH terms

  • Animals
  • Gastric Emptying / drug effects
  • Gastrointestinal Motility / drug effects*
  • Hydroxydopamines / pharmacology
  • Male
  • Methyltyrosines / pharmacology
  • Mice
  • Naloxone / pharmacology
  • Reserpine / pharmacology
  • Sympathectomy, Chemical
  • Sympatholytics / pharmacology
  • Thiazines / pharmacology*
  • Xylazine / pharmacology*
  • alpha-Methyltyrosine


  • Hydroxydopamines
  • Methyltyrosines
  • Sympatholytics
  • Thiazines
  • Xylazine
  • Naloxone
  • alpha-Methyltyrosine
  • Reserpine