IL-1-BETA-LIKE FREUNDS-ADJUVANT ENHANCES AXONAL-TRANSPORT OF OPIATE RECEPTORS IN SENSORY NEURONS

Chronic pain and inflammation increase substance P in sensory fibres o f peripheral nerves in which opiate receptors are known to undergo axo nal transport. The aim of the present study was to evaluate a possible modulation of axonal transport of opiate receptors in peripheral nerv es during inflammation. After intraplantar injection of Freund's adjuv ant to rats, the accumulation of mu and kappa opiate receptors increas ed on both sides of ligature in sciatic nerves of the injected paw. Th e contralateral side was unaffected and may serve as control. When IL- 1 beta was injected into rat paws, the axonal transport of opiate rece ptors was increased in a similar way. This suggests that IL-1 beta rep resents a major mediator to sensitize nociceptors during inflammation through a process requiring retrograde signals.