Topical mydriatics affect light-evoked retinal responses in anesthetized mice

Invest Ophthalmol Vis Sci. 2010 Jan;51(1):567-76. doi: 10.1167/iovs.09-4168. Epub 2009 Aug 6.


Purpose: To characterize effects of the muscarinic antagonist atropine (A) and the alpha-adrenergic agonist, phenylephrine (P), on mydriasis and light-evoked signaling in mice anesthetized by ketamine and xylazine (K+X).

Methods: Pupillary areas of anesthetized C57BL/6 mice were measured, with or without topical application of A or A+P. Dark-adapted ERGs were recorded from 2- to 4-month-old C57BL/6 and 7.5-month-old albino hrhoG/hrhoG mice after application of A or P singly or in combination, before or after induction of K+X anesthesia. Effects of GABA were tested in the hrhoG/hrhoG mice.

Results: K+X anesthesia resulted in maximum mydriasis that was not enhanced by A or A+P. Dark-adapted b-wave amplitudes (-1.3 log sc td s) after K+X anesthesia were similar with or without A or P. A+P in the presence of K+X produced a slow growth in b-wave amplitude, reaching a plateau of twofold enhancement in 1 hour. Recordings of responses to varying flash energies revealed that the effects of A+P were on the maximum amplitude of the a- and b-waves and not on their sensitivity. Scotopic threshold responses were augmented as well. In photoreceptor-degenerated mice (hrhoG/hrhoG), an electronegative ERG wave recorded with K+X+A, was converted to a gamma-aminobutyric acid (GABA)-sensitive response with two electropositive components with A+P after K+X.

Conclusions: Topical administration of A and P together, but not separately, in the presence of K+X, leads to a slow, dramatic enhancement of a- and b-waves by an unknown mechanism independent of pupil dilation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Topical
  • Adrenergic alpha-Agonists / administration & dosage
  • Anesthetics, Combined / administration & dosage*
  • Anesthetics, Dissociative / administration & dosage
  • Animals
  • Atropine / administration & dosage*
  • Dark Adaptation
  • Drug Combinations
  • Electroretinography / drug effects*
  • Ketamine / administration & dosage
  • Light
  • Mice
  • Mice, Inbred C57BL
  • Microscopy, Confocal
  • Muscarinic Antagonists / administration & dosage
  • Mydriatics / administration & dosage*
  • Phenylephrine / administration & dosage*
  • Pupil / drug effects*
  • Retina / radiation effects*
  • Retinal Degeneration / physiopathology
  • Time Factors
  • Xylazine / administration & dosage


  • Adrenergic alpha-Agonists
  • Anesthetics, Combined
  • Anesthetics, Dissociative
  • Drug Combinations
  • Muscarinic Antagonists
  • Mydriatics
  • Phenylephrine
  • Xylazine
  • Ketamine
  • Atropine