The central nervous system depressant effect of xylazine and xylazine-ketamine was studied in chicken and mice. Intraperitoneal injection of xylazine(1∼30㎎/㎏) and acylazine(1∼30㎎/㎏)-ketamine(100㎎/㎏) induced a loss of the righting reflex in chicken and mice, respectively, These effects of xylazine were dose-dependent.
The results obtained were as follows
1. The effect of xylazine-induced depression was antagonized by adrenergic antagonists having α₂-blocking activity(yohimbine, tolazoline, piperoxan and phentolamine).
2. Yohimbine was most effective in the reduction of the CNS depression by xylazine.
3. Phenoxybenzamine and prazosin did not reduced CNS depression by xylazine in both species.
4. Labetalol α₁, β₁-adrenergic antagonist) and propranolol (β-adrenergic blocking agent) were not effective in reducing xylazine induced depression.
5. Cholinergic blocking agents (atopine and mecamylamine ), a dopaminergic antagonist (Haloperidol), a histamine H₁-antagonist(chlorpheniramine), a histamine H₂-antagonist(cimetidine), a serotonergic-histamine H₁ antagonist(cyproheptadine) were not effective in reducing xylazine-induced depression.
6. Xylazine-induced depression is mediated by α₂-adrenergic receptors and appears not to be involved in cholinergic, dopaminergic, serotonergic or histaminergic pathways.
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