Pupillometry in mice: sex and strain-dependent phenotypes of pupillary functioning.
OBJECTIVE
Pupillometry is used as a phenotyping assay for investigating pupil responses in normal and genetically engineered mice. The mice used most often in contemporary ophthalmic research have not been adequately investigated by pupillometry.


METHODS
An infrared-video camera was used to assess pupillary functioning under standard dark-adapted conditions (30 min acclimatization in a ganzfeld chamber) and 30 min after the installation of either 10 microl tropicamide (1.0%) or 10 microl pilocarpine (5.0%) into the conjunctival cul-de-sac. The experiment was self-controlled using a repeated-measures analysis of variance to analyze 60 mice (30 males, 24 weeks of age) from three strains (C57BL/6, 129SvJ, and F1 hybrid).


RESULTS
The dark-adapted pupillary diameter of mice ranged from 2.3 mm (SD = 0.14) in female C57BL/6 to 2.9 mm (SD = 0.05) in male 129SvJ. Under dark-adapted conditions, all mice examined were sexual dimorphic (F = 19.5, dF = 2, 119, p < 0.001) and strain-dependent differences were observed between male C57BL/6-129SvJ and C57BL/6-F1 and female C57BL/6-F1 (F = 82.32, dF = 1, 119, p < 0.001). The mean pupillary diameter 30 min after the application of tropicamide ranged from 2.5 mm (SD = 0.16) in female F1 to 3.0 mm (SD = 0.13) in male C57BL/6. Tropicamide produced a sexual dimorphism in mydriasis for all mice (F = 56.30, dF = 1, 59, p < 0.001); however, strain-dependent differences were not observed (F = 1.31, dF = 2, 59, p < 0.280). The mean pupillary diameter 30 min after the application of pilocarpine ranged from 2.6 mm (SD = 0.28) in female C57BL/6 to 3.2 mm in both male F1 (SD = 0.22) and 129SvJ (SD = 0.04). Pilocarpine produced a sexual dimorphism in mydriasis for 129SvJ and F1 (F = 106.70, dF = 1, 59, p < 0.001) and strain-dependent differences were observed between female C57BL/6-F1 (F = 17.25, dF = 2, 59, p < 0.001).


CONCLUSIONS
The experiment demonstrates that mice respond idiosyncratically in their pupillary response under standard dark-adapted conditions and to either tropicamide or pilocarpine depending on strain and/or sex of the mouse. The characteristic responses observed are likely due to subtle differences in the genetic expression of phenotype.
Manno
Francis Anthony Michael
FA
Department of Biology, Virginia Wesleyan College, Norfolk, Virginia 23502-5599, USA. vitamus@gmail.com
D000818:Animals; D003623:Dark Adaptation; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains / Q000502:physiology*; D008916:Miotics / Q000494:pharmacology; D009184:Mydriatics / Q000494:pharmacology; D010641:Phenotype; D010862:Pilocarpine / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D015203:Reproducibility of Results; D012737:Sex Factors; D013045:Species Specificity; D014331:Tropicamide / Q000494:pharmacology
D008916:Miotics; D009184:Mydriatics; D010862:Pilocarpine; D014331:Tropicamide