Abstract
Medetomidine has been reported to decrease tear flow significantly in dogs, cats, and pigs when used as a sedative or analgesic; however, there are no such reports when it comes to rats. The present study aimed to investigate the effect of medetomidine on tear flow in rats. Medetomidine in doses of 50, 100, or 200 µg/kg or a physiological saline solution as the control, were administered intramuscularly to male Slc:Wistar/ST rats. After the administration of medetomidine, tear flow in both eyes was measured using a phenol red thread tear test. The area under the curve (AUC) of phenol red thread test values from baseline to 8 h was calculated. Data were plotted against the dose of medetomidine and simple linear regression analysis was performed. The effect of the drug on phenol red thread test values was considered dose-related when linear analysis yielded a significant relationship. In all medetomidine-treated groups, tear flow decreased significantly in both eyes after administration, while no significant changes were observed in either eye in the control group. The AUC values from baseline to 8 h after administration in groups treated with 100 and 200 µg/kg of medetomidine were significantly lower in both the left and right eyes compared to the control group. The linear regression of the AUC values was significant for both eyes. Our results indicated that the intramuscular administration of medetomidine in rats decreased tear flow significantly in a dose-dependent manner.
Highlights
Medetomidine, an α2 -adrenoceptor agonist, is widely used as a sedative or analgesic in veterinary medicine [1,2,3,4,5,6,7,8]
We aimed to investigate the effect of medetomidine on tear flow in rats
There were no differences in PRTT values between the left and right eyes in each time point for all groups
Summary
Medetomidine, an α2 -adrenoceptor agonist, is widely used as a sedative or analgesic in veterinary medicine [1,2,3,4,5,6,7,8]. Medetomidine and the other α2 -adrenoceptor agonists used alone or in combination with other drugs have potent sedative or analgesic effects, they have been reported to significantly decrease tear flow in dogs [28,29,30,31,32], cats [33,34], horses [35,36], and pigs [37]. Tear fluids play an essential role in maintaining the immune system of the ocular surface and the metabolic processes of the cornea, which is an avascular tissue
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