Spinal myelopathy induced by subarachnoid batrachotoxin: ultrastructure and electrophysiology

A combined structural and electrophysiologic analysis on the effects of subarachnoid injections of batrachotoxin was conducted in rats. Swelling of neuronal perikarya, accompanied by areas of clearing, satellitosis, fatty metamorphosis and central chromatolysis were demonstrated in the spinal anterior horns. Studies on isolated extensor digitorum longus (fast) and soleus (slow) muscles showed membrane depolarization in the extensor 24 h after injection, with progressive augmentation of this phenomenon in animals given multiple injections of the toxin. Differential sensitivity of fast and slow muscles was evident: soleus was only slightly affected. Subarachnoid injections of batrachotoxin, which induced swelling of neuronal perikarya and axonal processes, also caused signs of denervation in the extensor muscle 7 days after injection, while spontaneous transmitter release was still present. Some structural and and most electrophysiologic alterations after batrachotoxin injections were reversible.