C57BL/6 mice (Japan SLC, Inc., Shizuoka, Japan) were maintained in a standard 12 h light/dark environment (lights on at 7:00 A.M.). Food and water were available to mice ad libitum. All experimental procedures were performed in accordance with the National Institutes of Health Guidelines on the Care and Use of Animals and confirmed by the Himeji Dokkyo University Animal Experiment Committee. All efforts were made to minimize animal use and suffering.