Neuromuscular transmission in the mdx mouse.

In both disorders, the muscle fiber plasma membrane is rendered selectively vulnerable by dystrophin deficiency. In both disorders there are also ultrastructural abnormalities involving the postsynaptic membrane of the neuromuscular junction. The object of this electrophysiologic study was to determine whether the observed ultrastructural abnormalities at the mdx neuromuscular junction are associated with an abnormality of neuromuscular transmission. In comparison with age-matched control mice, the mdx mice show an abnormal, age-dependent decrease of the amplitude of the miniature end-plate potential and a concomitant increase in the quantal content of the end-plate potential. Consequently, the safety margin of neuromuscular transmission is not impaired.