Development and maintenance of tetrodotoxin-sensitive action potential in cultured skeletal muscle cells from dystrophic and normal chickens

Abstract

The maximum rate of rise of the tetrodotoxin (TTX)-sensitive spike was measured in 2-, 3-, and 4-week-old cultured myotubes from embryos of normal and dystrophic chickens. Similar increases in the maximum rates of rise of spikes were observed in normal and dystrophic cultures after 2 weeks of incubation with brain or embryo extract. Thereafter, these values were maintained in normal cultures, but decreased in dystrophic cultures. At both 3 and 4 weeks of age the values from dystrophic cultures were about 80% of those from normal cultures. These findings indicate that dystrophic chicken myotubes develop similarly to normal myotubes with respect to the TTX-sensitive spike-generating capability for the first 2 weeks in culture, and then diminish their capability which was once acquired. This reduced capability of cultured dystrophic myotubes might be indicative of a defect in the muscle cell membrane in muscular dystrophy. Furthermore, neither brain nor embryo extract from the dystrophic line was defective in supporting the development and maintenance of the TTX-sensitive spike-generating capability of cultured myotubes. This leads us to speculate that a myogenic rather than a neurotrophic phenomenon is responsible for our results.