LEUKEMIA INHIBITORY FACTOR INDUCES MECHANICAL ALLODYNIA BUT NOT THERMAL HYPERALGESIA IN THE JUVENILE RAT

Systemic administration or local injection to the rat hindpaw of leuke mia inhibitory factor induced a prolonged, dose dependent, mechanical hypersensitivity of the hindpaw flexion withdrawal reflex. Mechanical stimuli which were innocuous prior to leukemia inhibitory factor admin istration, evoked a rapid hindpaw withdrawal reflex indicative of mech anical allodynia. Pre-administration of anti-leukemia inhibitory facto r antibodies prevented this behavioural hypersensitivity. Hindpaw sens itivity to a noxious thermal stimulus was unaffected by leukemia inhib itory factor administration. Anti-leukemia inhibitory factor had no ef fect upon hindpaw withdrawal thresholds when injected alone nor influe nced the mechanical hypersensitivity produced by a subcutaneous inject ion of nerve growth factor. Injection of the closely related cytokine ciliary neurotrophic factor did not affect mechanical or thermal refle x withdrawal thresholds. Elevation of the neuroactive cytokine leukemi a inhibitory factor following peripheral nerve injury may be a contrib utory factor to the pathogenesis of neuropathic pain.