1. Department of Neuropsychopharmacology and Department of Neurobiology and Behavior, Behavior Research Institute, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371, Japan, Central Research Laboratories, Tsumura & Company, Ibaraki 300-11, Japan, and Department of Biochemistry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78284-7760