Dalip J. S. Sirinathsinghii and Ray G. Hill Merck, Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex CM20 2QR, UK There remains a distinct medical need for new pain therapies. Therefore, it is not surprising that in recent years there has been a major research initiative in both aca- demic and pharmaceutical laboratories to identify novel pain targets and to devel- op novel analgesic drugs. It is clear from numerous studies that the NMDA recep- tor plays a major role in the transmission ofnociceptive information and it has been a...