2.1 Animals and ethical approval
All of the animal procedures in this study are in accordance with the recommendations of the guidelines for the Care and Use of Laboratory Animals (1996. National Academy of Sciences. Washington, DC, USA), and were approved by the Ethical Committee of the Fudan University School of Basic Medical Sciences. Pathogen-free male Sprague–Dawley (SD) rats (seven-week old, 180 ± 10 g body weight) were purchased from the Experimental Animal Center of the Chinese Academy of Science in Shanghai. The animals were fed in cages with food and water available ad libitum , and housed in an air-conditioned room (22 - 25°C) illuminated from 07:00 to 19:00. Maximal efforts were made to minimize the number of animals and their suffering.