Transient cataract in rodents: an isolated phenomenon induced by ketamine–xylazine?

Abstract

Abstract: : Purpose: To report observations of reversible cataract in C57BL/6J mice and Brown–Norway (BN) rats undergoing general anesthesia with ketamine/xylazine and determine if ocular changes were associated to this phenomenon Methods: 7 to 9 weeks old C57BL/6J mice and BN rats were sedated with intraperitoneal injection of ketamine (120 mg/Kg for mice, 75 mg/Kg for rats) and xylazine (10 mg/Kg). Pupils were dilated with tropicamide 0.5% alone or in a combination with phenylephrine 2.5%, to allow access to the fundus, during laser procedure. Lens status was monitored by slit lamp biomicroscopy. Animals presenting lens opacification were excluded from the group undergoing laser and sacrificed at regular time intervals up to 3 hours corresponding to the onset, maximum and resolution of the cataract. Eyes were collected at these time points for retinal histology and immunocytochemistry. Antibody against glial fibrillary acidic protein was used to detect Müller cell response. Results: 65% of C57BL/6J mice and 55% of BN rats presented a cataract which occurred as early as 10 minutes (mice) or 30 minutes (BN rats) after the beginning of anesthesia. The cataract lasted up to 3 hours, time at which animals usually fully recovered from anesthesia. Lens opacification was more severe in mice, precluding the laser procedure. Müller cell reactivity, as demonstrated by GFAP immunostaining, was observed in the mid and peripheral regions of the retina. Conclusions: Cataract is a frequent complication of general anesthesia with ketamine/xylazine. To our knowledge, the pathomechanism of this cataract is unclear and despite its transient nature, can negatively impact the progress of the experimental procedure. Furthermore, lens changes were found to be also accompanied by retinal Müller cell reactivity. These observations mandate further investigation to provide a mechanism and develop preventive measures.

Keywords: drug toxicity/drug effects • microscopy: light/fluorescence/immunohistochemistry • pathology: experimental