Voltage-gated ion channels play a critical role in coupling excitation
at the neuromuscular junction to activation of contractile elements w
ithin a muscle fiber. Abnormal channel function can lead to either mus
cle paralysis or delayed relaxation. Recent advances in the molecular
characterization of these ion channels have provided the tools needed
to investigate the relationship between channel mutations and disorder
s of muscle excitability. This article reviews our current understandi
ng of muscle sodium, calcium, and chloride channels and their role in
the pathogenesis of myotonia and periodic paralysis. (C) 1997 Academic
Press.