NMDA-RECEPTOR CONTRIBUTION TO SPINAL NOCICEPTIVE REFLEXES - INFLUENCEOF STIMULUS PARAMETERS AND OF PREPARATORY SURGERY

The contribution of NMDA receptors to nociceptive reflexes has been as sessed both in awake rats and in electrophysiological tests on alpha-c hlorarose anaesthetized spinalized rats prepared with different degree s of surgery. Single motor unit activity was recorded in response to a lternating noxious mechanical and electrical stimuli applied to one hi ndpaw, and the results compared with paw pressure withdrawal reflexes in awake rats. There was little contribution by NMDA receptors to noci ceptive paw pinch responses either in awake rats or in rats prepared w ith minimal surgery, but following extensive lumbar surgery the contri bution increased significantly to a level similar to that seen in the wind-up component of responses elicited by electrical stimulation. Sur gery therefore has effects several segments from the sensory input tha t it generates. It enhances the NMDA receptor contribution in response s to some but not all types of afferent input. Copyright (C) 1996 Else vier Science Ltd.