Neuromuscular transmission is adequate in identified abnormal dystrophic muscle fibres

Abstract

IT has been suggested that ‘functional denervation’, a failure of structurally intact neuromuscular junctions to evoke a muscle fibre action potential following nerve stimulation, plays an important part in the pathogenesis of murine muscular dystrophy^1,2. Other workers, however, have been unable to confirm the existence of ‘denervated’ muscle fibres in dystrophic mouse muscle³. Moreover, the demonstration that transmitter release in response to nerve stimulation is normal in such muscle⁴ seems to preclude the possibility that ‘denervation’ may arise in an unpredictable or spasmodic way as a result of changes in transmitter store size or mobilisation during or after the repetitive discharge of the motoneurone. It has been considered possible, however, that the microelectrode techniques used in many of these studies do not always sample diseased muscle fibres, but select only a hypothetical group of ‘normal’ or ‘healthy’ muscle fibres. We have therefore applied a technique of intracellular staining^5,6 and demonstrated that structurally abnormal muscle fibres in dystrophic muscle display normal neuromuscular transmission.