For each data group, results were expressed as mean ± standard error of the mean (SEM), and n refers to the number of animals that were used. For statistical analysis, each treatment was compared with its respective control. Differences between two groups were assessed using the Student t-test. Differences between more than two groups were assessed using ANOVA. Differences were considered significant when P < 0.05. The statistical analyses were performed using GraphPad Prism 5.0 Software (GraphPad Software Inc., San Diego, CA, USA).