Mitsuhiro Isaka*, Reimi Hayashida, Yuumi Tamashima and Ryuji Araki
Department of Small Animal Clinical Sciences, School of Veterinary Medicine, Rakuno Gakuen University, 582 Bunkyodai Midorimachi, Ebetsu, Hokkaido 069-8501, Japan
Background: Dilated cardiomyopathy (DCM) is the most frequently diagnosed cardiomyopathy in rabbits. Timolol maleate (nonselective beta-blockers), which reduces the heart rate (HR) and blood pressure, has been used for glaucoma. However, this effect has not been assessed in a rabbit DCM model.
Aim: This study aimed to evaluate the circulatory effects of 0.5% timolol maleate eye drops in rabbit DCM models.
Methods: Rabbits were randomly divided into healthy (n = 8) and DCM rabbits (n = 8). Rabbit DCM models were established through intravenous administration of daunorubicin (4 mg/kg/week), an anthracycline anticancer drug, for 6 weeks. We measured the HR, mean arterial pressure (MAP), and echocardiography before (pre) and at 10, 30, 60, and 120 minutes after timolol maleate administration.
Results: Timolol maleate 0.5%eye drops significantly reduced the HR at 10, 30, and 60 minutes in DCM models and 10 minutes in healthy rabbits; however, there were no alterations in MAP. There was a significant fraction shortening elevation at 10 and 120 minutes in DCM models; moreover, there were marked ejection fraction elevations at all measurement points in only DCM models.
Conclusion: Timolol maleate eye drops exert several effects on the circulatory system in rabbit DCM models and healthy rabbits.
Keywords: Dilated cardiomyopathy, Eye drop, Rabbit, Timolol.