Ionic conductance and experimentally induced myotonia

Experiments were conducted to study the effect of altering external potassium on in vitro induction of myotonia in rat diaphragm using 2,4-dichlorophenoxy acetate (2,4-D). An increase in external potassium inhibited, while a decrease enhanced, the myotonic response. However, in preparations which have undergone prior denervation, there was no myotonic response to 2,4-D, even when the external potassium was lowered. The experiments also support the existence of neural factors influencing the resting ionic conductance of the muscle membrane.