The animals were treated in accordance with the Regulations of Experimental Animal Administration issued by State Committee of Science
and Technology of the People′s Republic of China on November 14,
1988. All animal experiments were carried out following protocols approved by the Institutional Animal Care and Use Committee of the
Shandong Agriculture University. Rats were kept at an ambient temperature of 22 ± 2 °C and relative humidity of 55 ± 5% withfixed 12 h
light-dark cycle and free access to standard rodent pellet diet and tap
water. After the experiments, rats were sacrificed by CO2inhalation