The action potential (AP) in most nerve and muscle preparations depends upon nanomolar concentrations of the neurotoxins saxitoxin (STX) and tetrodotoxin (TTX). In some excitable tissues lacking mature innervation, a toxin-resistant AP has been described by electrophysiological results. However, multiple attempts to detect corresponding toxin-resistant Na channels with radiolabelled STX and TTX have been unsuccessful. We report here the detection of Na channels with low-affinity binding of STX and TTX, accounting for 50-60% of the Na channels in rat hindlimb muscle 4-5 days after denervation.