Muscle fibre excitability and resting membrane potential in hamster muscular dystrophy

S U M M A R Y Measurements of resting potential carried out in vivo in the dystrophic hamster and also measurements of muscle excitability showed no difference between dystrophy and healthy animals. In murine muscular dystrophy, dystrophic muscle fibres have been found to have a lowered resting membrane potential, to give rise to spontaneous electrical potentials, and to have an increased excitability both to mechanical and electrical stimulation (Lenman, 1963; McComas and Mossawy, 1965, 1966). Reduced resting membrane potentials have also been recorded in human dystrophia myotonica (Hofmann et al., 1966; McComas and Mrozek, 1968) and in limb-girdle and facio-scapulo-humeral muscular dystrophy (Ludin, 1970). In 1975 Harris and Ward in a study of excised muscle from the hamster with genetic muscular dystrophy, which was first de-scribed in 1962 by Homburger and his associates, found a small reduction in resting membrane potential together with a reduced maximal rate of rise and overshoot amplitude of the action potentials in dystrophic muscle. In the present study we have recorded the resting membrane potential in vivo and also measured the excitability of muscle fibres in the dystrophic hamster. Methods Genetically dystrophic Syrian hamsters originating from the inbred strain described first by Hom-burger et al. (1962) and bred locally were used. Control animals were albino hamsters obtained from the Coomberhurst Breeding Establishment at Basingstoke. The animals varied in age from 22 to 26 weeks, and comparative measurements were made on control animals of comparable age. The animals were anaesthetised with pentobarbi-tone, and the exposed muscles of the right hin