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Philip C. Su, MD; Daniel S. Feldman, MD

Arch Neurol. 1973;28(6):376-379.

Abstract
An in vivo gracilis anticus preparation for microelectrode intracellular study of neuromuscular transmission was developed. The mean resting muscle fiber membrane potential was —73 mV. Resting miniature endplate potential (mepp) frequency was 2 to 4/sec in most fibers. Depolarization induced by external application of 20 millimolar K+ was slow in increasing mepp frequency. Frequency reached 100 to 150/sec rapidly with 35 millimolar K+. The potassium depolarization augmented mepp frequency was reduced up to 60% by increasing intravenous doses of diphenylhydantoin (DPH) up to 40 mg/kg with a median effective dose of 15 mg/kg. Depolarized muscle membrane potential was increased 15% after intravenously administered DPH. The DPH appears to stabilize the motor nerve terminal and muscle membrane. These actions may account for its effect in generalized myokymia and myotonia.

Author Affiliations
Brooklyn, NY

From the Division of Neurology, State University of New York, Downstate Medical Center, Brooklyn, NY. Dr. Feldman is now with the Medical College of Georgia Department of Neurology, Augusta. Dr. Su is with the Department of Neurology, College of Physicians and Surgeons, Columbia University, New York.

Footnotes
Accepted for publication Jan 11, 1973.

Reprint requests to Department of Neurology, College of Physicians and Surgeons, Columbia University, 710 W 168th St, New York 10032 (Dr. Su).

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