Possible role of apamin-sensitive K+ channels in myotonic dystrophy.
Myotonic muscular dystrophy is a genetic disease characterized mainly by muscle atrophy and myotonia, a repetitive electrical activity of muscle. In the present study, the possible role of apamin-sensitive K+ channels in the genesis of myotonia was investigated. Apamin is a peptide from bee venom that specifically blocks small conductance Ca(2+)-activated K+ channels. The injection of a small amount of apamin (20-30 microliters, 10 mumol/L) into the thenar muscle of myotonic dystrophy patients decreased the basal electrical activity during the electromyogram in the 6 patients studied. Myotonic discharges after muscle percussion were more difficult to trigger and of smaller intensity and duration. In 2 controls and in 2 patients with generalized myotonia, as well as in 1 patient with myotonia congenita (where the defect is in chloride channels), apamin had no effect. These results suggest that apamin-sensitive K+ channels participate in the mechanism that generates myotonia in myotonic dystrophy.
Behrens
M I
MI
Servicio de Neurología, Hospital Dr. Sótero del Río, Santiago, Chile.
Jalil
P
P
Serani
A
A
Vergara
F
F
Alvarez
O
O
D000328:Adult; D001030:Apamin / Q000494:pharmacology*; D004553:Electric Conductivity; D004576:Electromyography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
D015221:Potassium Channels; D001030:Apamin