GABA(A) RECEPTOR BLOCKADE INHIBITS A-BETA FIBER EVOKED WIND-UP IN THEARTHRITIC RAT

To clarify the mechanisms of allodynia we have examined whether 'wind- up' of nociceptive withdrawal reflexes (NWR), a phenomenon characteris tic of nociceptive C fiber spinal processing, can be mimicked by stimu lation of tactile A beta fibers in monoarthritic decerebrate spinal ra ts. Knee joint monoarthritis was induced by carrageenan/kaolin under h alothane anaesthesia 5 h before recordings. In arthritic, but not in c ontrol rats, wind-up of NWR of the semitendinosus muscle could be evok ed by repeated stimulation of A beta fibres. By contrast, peroneus lon gus reflexes did not exhibit marked windup. Bicuculline (0.03-0.3 mg/k g, i.v.) dose-dependently inhibited this wind-up. Hence, reflex wind-u p can be elicited by tactile A beta fibers in arthritic rats through a GABA, dependent mechanism. (C) 1998 Rapid Science Ltd.