EFFECTS OF LOCAL-ANESTHETICS ON CARRAGEENAN-EVOKED INFLAMMATORY NOCICEPTIVE PROCESSING IN THE RAT

We have assessed the effects of intraplantar local anaesthetics (bupiv acaine and lignocaine) on carrageenan-induced oedema, mechanical allod ynia and spinal c-fos protein expression. Mechanical allodynia was eva luated using the vocalization threshold to paw pressure (VTPP) every 3 0 min until 60, 180 or 240 min after administration of carrageenan. Pe ripheral oedema, mechanical allodynia and spinal c-fos protein express ion were maximal 180 min after carrageenan. Lignocaine did not influen ce either oedema or VTPP, but reduced spinal c-fos expression at 60 mi n after carrageenan without later effects. Bupivacaine induced an incr ease in VTPP at 30 and 60 min, limitation of oedema at 60 min and a re duction in spinal c-fos expression at 60 and 180 min, but these effect s were not present 240 min after carrageenan. Intraplantar infiltratio n with lignocaine and bupivacaine before carrageenan transiently limit ed signs of inflammatory pain but did not prevent them.