1. Graduate School of Bioagricultural Sciences (S.M., C.D., K.I., T.G., N.I., Y.U., H.T.), Nagoya University, Nagoya, Aichi 464-8601, Japan;
2. Center for Genetic Analysis of Behavior (M.S., M.H.), National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan;
3. Veterinary Medical Sciences (K.-i.M.), University of Tokyo, Tokyo 113-8657, Japan