title: Analysis of pupillary dilation produced by analogs of clonidine.
abstract: Pupillary responses to intravenous administration of clonidine and five congeneric derivatives of clonidine were observed in anesthetized cats. All of the agents tested produced a dose-dependent mydriasis of long duration. The order of potency for these compounds was clonidine (St-155) greater than St.375 greater than St-606 greater than St-608 greater than St-91. Pretreatment with yohimbine hydrochloride (0.5 mg/kg i.v.) shifted the dose-response curve for all of the compounds tested to the right. A CNS inhibition of parasympathetic nerve activity was demonstrated for clonidine and St-375 by means of direct recordings from the postganglionic ciliary nerves. An effect of high doses of St-91 on nerve activity was also observed. These results suggest that all the analogs of clonidine tested (with the possible exception of St-91) act like clonidine to produce mydriasis by a central alpha-adrenergic inhibition of parasympathetic outflow to the eye.
mesh_terms: D000818:Animals; D002415:Cats; D003000:Clonidine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D008297:Male; D009474:Neurons / Q000187:drug effects; D011680:Pupil / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D015016:Yohimbine; D003000:Clonidine