Effect of colchicine on neuropeptide Y expression in rat dorsal root ganglia and spinal cord

Neuropeptide Y (NPY) expression in the spinal cord and dorsal root ganglia (DRG) was examined after application of colchicine, an axonal transport blocker, on the intact sciatic nerve or prior to axotomy or chronic constriction injury (CCI). Rats that underwent topical application of colchicine on the sciatic nerve showed decreased responsiveness to heat stimulation, ipsilaterally. CCI-induced hyperalgesia was prevented by prior application of colchicine. However, colchicine did not block axotomy-induced NPY increase when applied proximally to the injury. In fact, colchicine induced the expression of NPY in the DRG and spinal cord in an identical manner to axotomy. The present data indicates that the increase in NPY observed after nerve injury could be initiated by the suppression of retrograde transport of factors, possibly neurotrophins, rather than by the production of an active factor at the site of injury.