A total of 48 male Sprague-Dawley rats (weighing, 180-220 g; 6-8 weeks of age) were purchased from the Animal Center of Guangzhou University of Chinese Medicine (Guangzhou, China). All animal procedures were approved by the Ethics Committee of Guangzhou University of Chinese Medicine and followed the regulations of the National Institute of Health Guide for the Care and Use of Laboratory Animals. All animals were acclimated for 7 days prior to surgery and were housed in a standard animal room (humidity, 50-70%; temperature, 21-25Δ°C) with a 12-h light-dark cycle and ad libitum access to food and water.