Analysis of pupillary dilation produced by analogs of clonidine |
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Authors: | Michael C. Koss |
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Affiliation: | Departments of Pharmacology and of Opthalmology and McGee Eye Institute, University of Oklahoma Health Sciences Center, P.O. Box 26901, Oklahoma City, Oklahoma 73190, U.S.A. |
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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 compound was clonidine (St-155) > St-375 > St-606 > St-600 > St-608 > 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 α-adrenergic inhibition of parasympathetic outflow to the eye. |
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Keywords: | Clonidine Clonidine analogs Ciliary nerve activity Yohimbine |
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