Effects of retrograde axonal transport of Ricinus communis agglutinin I on neuroma formation.

The lectin Ricinus communis agglutinin I (RCAI) was topically applied to transected mouse sciatic nerve or to neuromas formed 2 months after a nerve transection. Fluorochrome-labelled ricin was transferred to the corresponding dorsal root ganglia where it accumulated selectively in the nerve cells, apparently as a consequence of retrograde axonal transport. The ricin caused an almost total loss of the dorsal root ganglionic neurons and, consequently, could prevent formation of neuromas or eliminate an already existing neuroma. The hybrid toxin wheat germ agglutinin (WGA)-ricin-A chain caused no apparent increased sensitivity for neuronal destruction. The drugs doxorubicin and ethidium bromide, similarly applied, labelled satellite and other cells in addition to neurons in the ganglia, and caused only a moderate neuronal loss. The presented method to eliminate neuromas by selectively destroying sensory neurons may provide a means to study pain mechanisms in neuromas.