Reduction of experimental neuroma formation with ricin

Twenty rat sciatic nerves were bilaterally transected, one as control, and one intraneurally injected with ricin. At 11 weeks, all controls demonstrated large neuromas. Ten injected nerves had no neuroma or a significantly smaller one, while the other 10 had neuroma formation similar to controls. No effect on distant dorsal root ganglia or spinal cord was seen. Thirteen additional rats underwent nerve injection with I125-labeled ricin. At one week, most radioactivity was localized to sciatic nerve, surrounding muscle, and thyroid, with trace amounts in dorsal root ganglia and spinal cord. Intraneural ricin can inhibit neuroma formation in transected nerve, but results in unpredictable uptake of ricin by nerve and excess spillage into surrounding tissues.