Abstract Batrachotoxin (BTX) when applied to a nerve results in a block of impulse transmission and axonal transport whereas tetrodotoxin (TTX) blocks only impulse transmission. After chronic application of these toxins to the rat tibial nerve for 20 to 40 days, the total soluble protein content and the activity of lactate dehydrogenase (LDH), creatine kinase (CK), pyruvate kinase (PK), as well as the heme content, decreased in the soleus muscle. The response after denervation was similar to but greater than that obtained with BTX. Gel electrophoresis of the enzymes showed a change in the isoenzyme pattern of LDH1 and LDH5, PK-M1 and PK-M2 in the soleus after BTX or denervation. In sharp contrast to BTX and denervation, TTX caused only a slight reduction in LDH1. No change was observed in the soleus creatine kinase isoenzyme pattern after denervation or neural application of BTX or TTX.