title: Optic nerve vasomotor effects of topical beta-adrenergic antagonists in rabbits.
abstract: OBJECTIVE
  To examine the anterior optic nerve vasomotor effects of nonselective and relatively beta-1-selective beta-adrenergic antagonists in rabbits, because different influences on optic nerve blood flow with these medications have been suggested.
  
  
  METHODS
  After topical therapy for 30 days with either timolol maleate 0.5% (six rabbits), betaxolol hydrochloride 0.5% (six rabbits), or placebo (two rabbits), the microvasculature of the optic nerve was examined with an intraluminal microvascular corrosion casting technique. The investigators were masked to both the medication group and the treated eye. The constriction, in percent of the downstream vessel caliber, was measured at the vascular branching point of arterioles supplying the anterior optic nerve. An average constriction was calculated and compared between the medication groups and between the treated and the contralateral, untreated eyes.
  
  
  RESULTS
  Constriction values from a total of 218 arterioles supplying the anterior optic nerve were obtained for the 14 rabbits. The means of the average constriction on the treated side were comparable between the groups treated with timolol maleate, betaxolol hydrochloride, and placebo (one-way analysis of variance, P = .64), as well as between the treated and untreated eyes (two-tailed t-test for paired variables, P = .68 for timolol maleate and P = .42 for betaxolol hydrochloride). The statistical power to find a difference of 5% or more average constriction was at least 90%.
  
  
  CONCLUSIONS
  Both relatively selective and nonselective beta-adrenergic antagonists produce no observable optic nerve vasomotor effects in the rabbit eye.
authors.affiliation: Devers Eye Institute/R. S. Dow Neurological Science Institute/Legacy Portland Hospital, Oregon, USA.
authors.forename: S
authors.initials: S
authors.lastname: Orgül
authors.forename: S
authors.initials: S
authors.lastname: Mansberger
authors.forename: D R
authors.initials: DR
authors.lastname: Bacon
authors.forename: E M
authors.initials: EM
authors.lastname: Van Buskirk
authors.forename: G A
authors.initials: GA
authors.lastname: Cioffi
mesh_terms: D000287:Administration, Topical; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001160:Arterioles; D015784:Betaxolol / Q000008:administration & dosage / Q000494:pharmacology*; D016319:Corrosion Casting; D005260:Female; D007429:Intraocular Pressure; D008297:Male; D008833:Microcirculation; D009883:Ophthalmic Solutions; D009900:Optic Nerve / Q000098:blood supply* / Q000473:pathology; D011817:Rabbits; D013999:Timolol / Q000008:administration & dosage / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*; D014666:Vasomotor System / Q000187:drug effects* / Q000473:pathology
chemical_list: D000319:Adrenergic beta-Antagonists; D009883:Ophthalmic Solutions; D013999:Timolol; D015784:Betaxolol