Objective To investigate the roles of peripheral extracellular signaling-regulated kinases 1/2 (ERKs) pathway in melittin-induced pain-related behaviors and responses of spinal wide-dynamic-range (WDR) neurons,a population of "central encoder" along the spinally-organized sensorimotor (SOSM) reflex circuitry.Methods In behavioral experiments,persistent spontaneous nociceptive behavioral response of rats was determined by counting the number of paw flinches during each 5 min interval for 1 h following s.c.melittin injection.Heat and mechanical hypersensitivity were measured with TC-1 radiant heat stimulator and ascending graded von Frey monofilaments,respectively.In electrophysiological experiments,typical WDR neurons characterized by increased spike firing rate to brush,pressure and noxious pinch were applied to the peripheral receptive field.