BRIEF ELECTRICAL-STIMULATION OF C-FIBERS IN RATS PRODUCES THERMAL HYPERALGESIA LASTING WEEKS

Nerve injury produces neuropathic pain in some humans, but the nature of the signal triggering the pain is still unknown. When injured, many afferent fibers emit a prolonged discharge of action potentials. This input triggers pain disorders in rats following some, but not other t ypes of total and partial nerve injury. In the present study we report that similar sensory disorders develop in rats by electrically stimul ating an intact sciatic nerve. Robust thermal hyperalgesia and weak me chanical allodynia developed rapidly, lasting 3-5 weeks thereafter, bu t only when activating C-fibers. Thus, a discharge mimicking injury di scharge in C-fibers, in the absence of any intended damage to the stim ulated nerve, is sufficient to alter chronically central processing of sensory input. (C) 1998 Elsevier Science Ireland Ltd.