title: Antagonism of xylazine plus chloral hydrate loss of the righting reflex in mice. A simple in vivo procedure for the evaluation of selective alpha 2-adrenoceptor antagonists.
abstract: Xylazine causes a dose-related loss of the righting reflex (LRR) in mice when combined with a subanesthetic dose of chloral hydrate. Compounds that preferentially block alpha 2-adrenoceptors antagonize this xylazine plus chloral hydrate LRR at low doses and in a dose-related manner. This action of these compounds appears related to their alpha 2-adrenoceptor blocking properties insofar as their activity in this test correlates reasonably well with their activity in other in vivo and in vitro procedures thought to reflect alpha 2-antagonism. Also, compounds without any appreciable alpha blocking properties or without selectivity for blocking alpha 2-adrenoceptors are not active in this procedure. At higher doses, the alpha 2-blockers antagonize the reversal of the LRR caused by low doses. This action may be indicative of the in vivo alpha 1 blocking properties of these compounds, which may in turn be related to their sedating properties. In any event, antagonism of xylazine plus chloral hydrate LRR in mice appears to be a simple, rapid, and quantitative procedure for the in vivo evaluation and comparison of selective alpha 2-adrenoceptor antagonists.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D002697:Chloral Hydrate / Q000037:antagonists & inhibitors*; D004146:Dioxanes / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D019329:Idazoxan; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D004856:Postural Balance / Q000187:drug effects*; D011807:Quinolizines / Q000494:pharmacology; D012018:Reflex / Q000187:drug effects*; D013843:Thiazines / Q000037:antagonists & inhibitors*; D014991:Xylazine / Q000037:antagonists & inhibitors*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D011807:Quinolizines; D013843:Thiazines; D014991:Xylazine; D015016:Yohimbine; D002697:Chloral Hydrate; C038538:Wy 26703; D019329:Idazoxan