All animal care and experiments were conducted in accordance with the institutional guidelines of the Animal Committee of Tokyo Medical and Dental University. Thirty-six wild type male Wistar rats (Charles River Laboratories Japan, Kanagawa, Japan) from the ages of ten to eleven weeks were used for the experiments. The weight ranged between 294-342 g. Rats were housed under a 12-h light–dark cycle and allowed food and water ad libitum.