title: Preventing Corneal Calcification Associated With Xylazine for Longitudinal Optical Coherence Tomography in Young Rodents.
abstract: Spectral-domain optical coherence tomography (SD-OCT) is widely used in clinical ophthalmology and recently gained popularity in laboratory research involving small rodents. Its noninvasive nature allows repeated measurements, thereby decreasing the number of animals required. However, when used at a conventional dosage, xylazine (an α2-adrenoceptor) can cause irreversible corneal calcification, especially among young rodents. In the present study, we test whether corneal calcification associated with xylazine is mediated by the α2-adrenoceptor.
  
  
  
  Our study tested Sprague-Dawley rats, Long-Evans rats, and CD-1 mice (postnatal day [P]14). Retinal images were captured by SD-OCT. Quantitative PCR (qPCR) was used to study gene expression, whereas receptor localization was examined by immunofluorescent staining followed by confocal microscopy. Calcium deposits were detected via von Kossa staining.
  
  
  
  When used at dosages appropriate for adult animals, ketamine-xylazine anesthetics led to a high rate of respiratory failure, increased apoptotic activity in the corneal epithelium, and irreversible corneal calcification in P14 rat pups. Meanwhile, OCT image quality decreased drastically as a result of corneal calcification among animals recovering from anesthesia. α2-Adrenoceptor subtypes were highly expressed on P14, in line with rodents' age-specific sensitivity to xylazine. Clonidine, a potent α2-adrenoceptor agonist, dose-dependently induced corneal calcification, which could be prevented by an α2-adrenoceptor antagonist.
  
  
  
  These data suggest that α2-adrenoceptors contribute to corneal calcification in young rodents. Therefore, we developed a suitable OCT imaging protocol for this cohort, including a carefully tailored ketamine-xylazine dosage (60 mg/kg and 2.5 kg/mg, respectively).
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada 2Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada.
authors.forename: Tianwei Ellen
authors.initials: TE
authors.lastname: Zhou
authors.affiliation: Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada 3École d'Optométrie, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Diane N
authors.initials: DN
authors.lastname: Sayah
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada 2Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada.
authors.forename: Baraa
authors.initials: B
authors.lastname: Noueihed
authors.affiliation: Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada 4Department of Ophthalmology, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Javier
authors.initials: J
authors.lastname: Mazzaferri
authors.affiliation: Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada 4Department of Ophthalmology, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Santiago
authors.initials: S
authors.lastname: Costantino
authors.affiliation: Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada 4Department of Ophthalmology, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Brunette
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada 2Hôpital Maisonneuve-Rosemont Research Center, Montréal, Québec, Canada 4Department of Ophthalmology, Université de Montréal, Montréal, Québec, Canada 5Department of Pharmacology, Centre Hospitalier Universitaire Sainte-Justine Hospital, University of Montréal, Montréal, Québec, Canada 6Department of Pediatrics, Centre Hospitalier Universitaire Sainte-Justine Research Center, Université de Montréal, Montréal, Québec, Canada.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Chemtob
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000633:toxicity; D000818:Animals; D002114:Calcinosis / Q000473:pathology / Q000517:prevention & control*; D002118:Calcium / Q000378:metabolism; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D003316:Corneal Diseases / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007150:Immunohistochemistry; D051379:Mice; D018613:Microscopy, Confocal; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D041623:Tomography, Optical Coherence / Q000379:methods*; D014991:Xylazine / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D014991:Xylazine; D002118:Calcium