Completeness and selectivity of ricin "suicide transport" lesions in rat dorsal root ganglia.

Ricinus communis agglutinin (MW 60 kDa type, RCA60, ricin) injected into the rat sciatic nerve produces massive degeneration of cells in those dorsal root ganglia (DRGs) known to contain the sensory cells-of-origin of the sciatic nerve. We have evaluated the extent of this cell death quantitatively. Using 1 or 2 micrograms RCA60, the average proportion of L5 DRG neurons destroyed closely matched the proportions of neurons in this ganglion known to have an axon in the sciatic nerve. A lower dose, 0.2 microgram ricin, produced substantially less cell death. There was heavy fiber degeneration in the sciatic nerve proximal to the injection site, but not in a nearby tributary nerve with which it shares the L5 DRG. Furthermore, the topographic distribution of Fink-Heimer argyrophilia corresponded to the known sciatic nerve distribution. The data suggest that at appropriate doses toxic ricin can produce a near complete and selective lesion by retrograde "suicide transport".