Antisecretory activity of the alpha2-adrenoceptor agonist, xylazine in rat jejunal epithelium

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Abstract
Xylazine, an α2 adrenoceptor agonist, reduces short circuit current (SCC) in epithelial preparatior of rat jejunum. The α2 antagonist yohimbine, abolishe this response while prazosin was without effect The cyclooxygenase inhibitor, piroxicam, also attenuate xylazine responses indicating that the antisecretory effect were dependent upon endogenous eicosanoid formation. the secretory state of piroxicam treated tissues was restore by addition of either forskolin, vasoactive intestinal poll peptide (VIP), prostaglandin E2 (PGE2) or isobutyl-: methyl-xanthine (IBMX) then subsequent additions of xylazine were effective in reducing SCC. All these agents are known to increase SCC and cause Cl secretion by elevating intracellular cAMP. In addition, xylazine was also able to inhibit the Ca2+-mediated secretory responses of carbachol (CCh) and substance P (SP) in rat jejunum. This ability of xylazine to inhibit CAMP- and Ca2+-mediated secretion may indicate that α2 adrenoceptors interact with more than or type of G protein or alternatively suggests a more general interaction between second messenger systems withiin epithelia of the small intestine.