The effect of intrathecally administered imiloxan and WB4101: possible role of alpha 2-adrenoceptor subtypes in the spinal cord.
To define the antagonist pharmacology of spinal antinociceptive effects of alpha 2-adrenoceptor agonists, the ability of WB4101 (2-(2,6-dimethoxyphenoxyethyl)-aminomethyl-1,4-benzodioxane) and imiloxan to antagonize the effect of spinal ST-91 (2-[2,6-diethylphenylamino]-2-imidazoline), clonidine and dexmedetomidine was examined. Antinociceptive effects of ST-91 were antagonized by WB4101 and imiloxan; clonidine only by WB4101; and, dexmedetomidine was not antagonized by either antagonist. It is hypothesized that the alpha 2 adrenoceptor subtype alpha 2A is involved in the antinociception of spinal clonidine and dexmedetomidine, and alpha 2B is involved in that of ST-91.
Anesthesiology Research Laboratory, University of California, San Diego, La Jolla 92093.
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D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D004146:Dioxanes / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007278:Injections, Spinal; D008297:Male; D020926:Medetomidine; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000032:analysis / Q000502:physiology*; D013116:Spinal Cord / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D007093:Imidazoles; D011942:Receptors, Adrenergic, alpha; C011266:ST 91; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; D003000:Clonidine; D020926:Medetomidine; C044484:Imiloxan