Distal reduction of the conduction velocity of α-axons in tullidora (buckthorn) neuropathy

Abstract

Cats were given a single oral dose of ether extracts of the tullidora ( Karwinskia humboldtiana) fruit. Three to five weeks later these animals developed the tullidora (buckthorn) neuropathy. Acute experiments were conducted in control cats as well as in treated cats which showed hind limb paralysis. Spinal motoneurons of the medial gastrocnemious and the soleus nerves were recorded intracellularly and their axons were electrically stimulated at two points, near the entry to the muscle and at the hip level. The conduction velocity was determined for the segment between the two stimulating electrodes [distal conduction velocity; (DCV)] and for the segment between the electrode at the hip level and the spinal cord [proximal conduction velocity (PCV)]. In untreated animals, DCV was higher than PCV so that the ratio DCV:PCV was, on the average, larger than 1. In treated animals, DCV was reduced, but PCV remained within normal limits and DCV:PCV was lower than 1. In addition, there was a relative deficit of the faster velocities suggesting that the thicker fibers were preferentially affected. These observations are in agreement with previous ones indicating that demyelination induced by tullidora is restricted to distal nerve segments.