Studies of alpha-adrenoceptor antagonists on sympathetic mydriasis in rabbits

Yongxin Yu, Michael C Koss

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


This study was undertaken to identify the alpha-adrenergic receptor type responsible for sympathetically evoked mydriasis in pentobarbital-anesthetized rabbits. Frequency-response curves of pupillary dilation were generated by stimulation of the preganglionic cervical sympathetic nerve (1-64 Hz). Evoked mydriatic responses were inhibited by systemic administration of nonselective alpha-adrenergic antagonists, phentolamine (0.3-10 mg/kg) and phenoxybenzamine (0.03-0.3 mg/kg), as well as the selective alpha(1)-adrenergic antagonist, prazosin (0.1-1 mg/kg). The alpha(2)-adrenergic antagonist, RS 79948 (0.3 mg/kg, i.v.) was without inhibitory effect, but potentiated the mydriatic response. In addition, the selective alpha(1A)-adrenoceptor antagonist, 5-methylurapidil (0.1-1 mg/kg, i.v.), antagonized the elicited mydriasis in a dose-dependent fashion. Unlike previous observations that prazosin does not block the adrenoceptor in rabbit iris dilator muscle, our results suggest that prazosin is effective in inhibiting neuronally elicited mydriasis in this species, and that alpha(1A)-adrenoceptors appear to mediate the response.
Original languageEnglish
Pages (from-to)255-63
Number of pages9
JournalJournal of Ocular Pharmacology and Therapeutics
Issue number3
Publication statusPublished - Jun 2003


  • Adrenergic alpha-1 Receptor Antagonists
  • Adrenergic alpha-2 Receptor Antagonists
  • Adrenergic alpha-Antagonists
  • Animals
  • Dose-Response Relationship, Drug
  • Electric Stimulation
  • Isoquinolines
  • Male
  • Mydriasis
  • Mydriatics
  • Naphthyridines
  • Phenoxybenzamine
  • Phentolamine
  • Piperazines
  • Prazosin
  • Pupil
  • Rabbits
  • Sympathetic Nervous System

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