2.1 Animals
Adult male C57BL/6J mice (9 weeks old) and male CD1 mice (50 weeks old) were obtained from the Experimental Animal Center of Medical College, Nanchang University. Before being used, mice were housed five per cage under standard conditions (12 hours light/dark cycle; lights on from 7:00 to 19:00; 23±1°C ambient temperature; 55±10% relative humidity; bedding replacement twice a week) for 1 week with free access to food and water. Each experimental group consisted of 20 mice and behavioral experiments were performed during the light phase. A total of 900 mice were used in these experiments. For animal sacrifice, all mice were first anaesthetized using 0.5% pentobarbital sodium (10mL kg-1) and then killed by cervical dislocation. All animal care and experimental protocols were conducted in compliance with the Guide for the Care and Use of Laboratory Animals (8th edition, Institute of Laboratory Animal Resources on Life Sciences, National Research Council, National Academy of Sciences, Washington DC) and the guidelines of the Animal Care and Use Committees of Nanchang University, China. The animals were left undisturbed for at least one week between testing when used in multiple models. The home cages were brought into the test room at least 30 min before each experiment.