COLCHICINE TREATMENT OF THE SCIATIC-NERVE REDUCES NEUROGENIC EXTRAVASATION, BUT DOES NOT AFFECT NOCICEPTIVE THRESHOLDS OR COLLATERAL SPROUTING IN NEUROPATHIC OR NORMAL RATS

The effect of topical colchicine treatment of the sciatic nerve on sci atic and saphenous nociceptive thresholds and neurogenic extravasation was investigated in normal and neuropathic rats. After a pilot invest igation using several different concentrations of colchicine it was de termined that treating the sciatic nerve with 5 mM colchicine did not usually affect the heat nociceptive threshold over the sciatic innerva ted plantar surface of the hindpaw. Mechanical nociception and motor f unction were also unchanged. Electrical stimulation of the sciatic ner ve after intravenous injection of Evans blue dye causes extravasation of the dye in the cutaneous distribution of the nerve. The area and qu antity of sciatic extravasation were measured 3 weeks after treating t he sciatic nerve with colchicine. This treatment results in a marked l oss of neurogenic extravasation, but there were no changes in the scia tic and saphenous mediated heat and mechanical nociceptive thresholds. The area of saphenous nociceptive innervation was mapped using Finch responses and saphenous neurogenic extravasation acutely after sciatic section. There was no change in the cutaneous distribution of sapheno us nociceptive fibers when measured 3 weeks after the sciatic colchici ne treatment. Some rats had their sciatic nerves transected immediatel y after colchicine treatment (5 and 50 mM) and the saphenous nocicepti ve thresholds and autotomy scores were followed postoperatively. Colch icine pretreatment of the sciatic nerve has no effect on the developme nt of hyperalgesia or autotomy. Colchicine blocks axonal transport in peripheral nerve, including the orthograde transport of tachykinins, w hich probably explains its ability to induce prolonged reductions in s ciatic neurogenic extravasation at concentrations that spare C-fiber n ociceptor function. Sciatic nerve colchicine treatment does not trigge r nociceptive fiber collateral sprouting from the adjacent saphenous n erve, nor does it influence the development of hyperalgesia and autoto my behavior after sciatic transection. (C) 1998 International Associat ion for the Study of Pain. Published by Elsevier Science B.V.