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Colonic α2‐adrenoceptor‐mediated responses in the pony
Author(s) -
ROGER T.,
RUCKEBUSCH Y.
Publication year - 1987
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.1987.tb00107.x
Subject(s) - detomidine , xylazine , tolazoline , pony , chloralose , endocrinology , stimulation , medicine , chemistry , tonic (physiology) , prostaglandin , anesthesia , biology , ketamine , genetics
Roger, T. & Ruckebusch, Y. Colonic α2‐adrenoceptor‐mediated responses in the pony. J. vet. Pharmacol. Therap. 10 , 310–318. The motor responses of the caecum and colon to stimulation of α2‐adrenoceptors by xylazine and detomidine at the recommended dose levels of 0.6 and 0.1 mg/kg were investigated in three ponies. The motor changes of the left ventral colon induced by continuous intra‐arterial infusion of a prostaglandin (PGF 2α ) were used to assess the relative inhibitory effects of xylazine and detomidine in a colic model. The administration of α 2 ‐agonists inhibited the spiking activity on the whole of the large intestine for 20–30 min (xylazine) or 2–3 h (detomidine). However, the detomidine‐induced inhibition was preceded by a short period of increased smooth muscle basal tone as indicated by strain‐gauge force transducer measurements. This pattern of activity was neither reversed nor prevented by the administration of tolazoline (10 μg/kg/min) intra‐arterially. In contrast, inhibition of the colonic phasic and tonic motor activity by α‐adrenoceptor stimulation was reversed competitively by tolazoline. The intra‐arterial infusion of prostaglandin F 2α (10 μg/kg/min) induced prolonged and sustained spiking activity that might be related to signs of mild colic. Detomidine, and to a lesser extent xylazine, relaxed the whole of the large intestine and this was accompanied by alleviation of the signs of visceral pain.