Anatomically selective peripheral nerve ablation using intraneural ricin injection

Anatomically selective destruction of sensory and motor neurons based upon which nerve contains the corresponding axons can be accomplished by intraneural pressure microinjection of the toxic lectin, ricin. Ricin is taken up by axons at the injection site and axonally transported to perikarya resulting in destruction of the neurons. In the present report, we describe a reliable procedure for making such lesions using pressure microinjection of ricin into nerve trunks. Consistent, complete lesions restricted to the appropriate sensory and motor neurons are documented after injection of the vagus, hypoglossal, phrenic and sciatic nerves and the superior cervical ganglion. Complete vagal ablations could be achieved with 100 ng or less of ricin; whereas, 1-3 micrograms was required to obtain similar results with hypoglossal and sciatic nerves. Although most neurons are dead within 24 h after the injection, survival times of 10-14 days may be necessary for complete disappearance of poisoned neurons. This technique can be valuable in making highly selective lesions for anatomical, neurochemical and neurophysiological experiments.