Pii: s0165-1781(00)00191-8
Piyarat Govitraponga,U, Jaturaporn Chagkutipa, Wanpena Neuro-Beha ¨ ioural Biology Center, Institute of Science and Technology for Research and De ¨ elopment, Mahidol Uni ¨ ersity, Salaya, Nakornpathom 73170, Thailand b Department of Psychiatry, Faculty of Medicine, Srinakarinwirot Uni ¨ ersity, Bangkok, Thailand c Department of Physiology, Faculty of Medicine, Chulalongkorn Uni ¨ er