title: Investigation of capsaicin-induced superficial punctate keratopathy model due to reduced tear secretion in rats.
abstract: OBJECTIVE
  The present study investigated the usefulness of the superficial punctate keratopathy (SPK) model due to reduced tear secretion induced by the injection of capsaicin in neonatal rats.
  
  
  METHODS
  On postnatal day 4, rats were injected subcutaneously with a single dose of capsaicin. Ocular surface symptoms were evaluated by measuring corneal sensitivity, tear secretion and corneal fluorescein score. Furthermore, the effect of pilocarpine was investigated by measuring tear secretion and corneal fluorescein score in this model. The influence of discontinuation of pilocarpine application was also examined.
  
  
  RESULTS
  Capsaicin caused a dose-dependent reduction of tear secretion and increase of corneal fluorescein score. In addition, 50 mg/kg capsaicin-treated rats showed a sustained decrease of corneal sensitivity and tear secretion, and an increase of corneal fluorescein score compared with vehicle-treated rats. Moreover, capsaicin-treated rats showed SPK. Instillation of pilocarpine significantly increased tear secretion and tended to improve the corneal fluorescein score by repeated application, whereas tear secretion and corneal fluorescein score in the pilocarpine-treated rats returned to the same level as that of capsaicin-treated rats after discontinuation of pilocarpine application.
  
  
  CONCLUSIONS
  Injection of capsaicin in rats induced stable SPK due to reduced tear secretion accompanied by a decrease of corneal sensitivity. Thus, it may be concluded that this model is essentially similar to SPK due to reduced tear secretion and could be used in the development of appropriate new drugs for therapy.
authors.affiliation: Division of Dermatologicals and Ophthalmologicals, Ako Research Institute, Otsuka Pharmaceutical Co. Ltd., Hyogo, Japan. kagawa.yoto@otsuka.jp
authors.forename: Yoto
authors.initials: Y
authors.lastname: Kagawa
authors.forename: Shinsaku
authors.initials: S
authors.lastname: Itoh
authors.forename: Hisashi
authors.initials: H
authors.lastname: Shinohara
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000633:toxicity*; D003316:Corneal Diseases / Q000139:chemically induced* / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015352:Dry Eye Syndromes / Q000139:chemically induced* / Q000378:metabolism; D005260:Female; D019793:Fluorescein / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D007279:Injections, Subcutaneous; D007765:Lacrimal Apparatus / Q000187:drug effects* / Q000378:metabolism; D008916:Miotics / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D018689:Sensory System Agents / Q000633:toxicity*; D013666:Tears / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D008916:Miotics; D018689:Sensory System Agents; D010862:Pilocarpine; D002211:Capsaicin; D019793:Fluorescein