Action potential generation in denervated rat skeletal muscle. II. The action of tetrodotoxin.

Abstract

AbstractAction potential generation was studied in the presence of tetrodotoxin (TTX) up to one week after denervation in individual muscle fibres of the extensor digitorurn longus and diaphragm muscles of the rat. TTX 10‐6 M completely blocked spike generation in innervated inuscle and in niuscle denervated for one day. On the second and subsequent days after denervation, action potentials resistant to TTX were recorded in the muscle fibres. In the extensor digitorum longus muscle denervated for 5 days, action potentials recorded in the presence of TTX 10‐6 M had a mean rate of rise 250 V/sec, and they exceeded the zero membrane potential by an average of 28 mV. This TTX resistant action potential generation was impaired by reducing the external sodium concentration, and abolished in the absence of that cation. A correlation was obsrrved between the presence of TTX resistant action potentials and the acetylcholine sensitivity of the muscle membrane.