Preventing corneal calcification associated with xylazine for longitudinal optical coherence tomography in young rodents
Article [Version of Record]
Is part of
Investigative ophthalmology and visual science ; vol. 58, pp. 461-469.Publisher(s)
Association for research in vision and ophthalmologyAuthor(s)
Abstract(s)
PURPOSE. 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 a2-
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 a2-adrenoceptor.
METHODS. 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.
RESULTS. 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. a2-Adrenoceptor subtypes were highly expressed on P14, in line with rodents’
age-specific sensitivity to xylazine. Clonidine, a potent a2-adrenoceptor agonist, dosedependently induced corneal calcification, which could be prevented by an a2-adrenoceptor
antagonist.
CONCLUSIONS. These data suggest that a2-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).