TY - JOUR
T1 - Axonal hyperpolarization associated with acute hypokalemia
T2 - Multiple excitability measurements as indicators of the membrane potential of human axons
AU - Kuwabara, Satoshi
AU - Kanai, Kazuaki
AU - Sung, Jia Ying
AU - Ogawara, Kazue
AU - Hattori, Takamichi
AU - Burke, David
AU - Bostock, Hugh
PY - 2002
Y1 - 2002
N2 - Multiple nerve excitability measurements have been proposed for clinical testing of nerve function, and an important determinant of excitability is membrane potential. We report a patient with acquired hypokalemic paralysis in whom multiple excitability indices (stimulus -response curve, strength-duration properties, threshold electrotonus, recovery cycle) were measured during and after an acute hypokalemic attack (serum K+ level, 2.1 mEq/L and 4.5 mEq/L, respectively). During hypokalemia, there was a shift of the stimulus-response curve to the right, a decrease in strength-duration time constant, a "fanning-out" of responses during threshold electrotonus, a reduction in relative refractory period, and an increase in superexcitability; all of these indicate axonal hyperpolarization, presumably due to the K+ equilibrium potential being more negative. These indices returned to normal 20 h later, associated with normalization of the serum K+ level. These results demonstrate that the changes associated with hypokalemic paralysis are not confined to muscle and that axons undergo hyperpolarization in vivo. Multiple excitability measurements can be used as a tool to identify changes in membrane potential of human axons.
AB - Multiple nerve excitability measurements have been proposed for clinical testing of nerve function, and an important determinant of excitability is membrane potential. We report a patient with acquired hypokalemic paralysis in whom multiple excitability indices (stimulus -response curve, strength-duration properties, threshold electrotonus, recovery cycle) were measured during and after an acute hypokalemic attack (serum K+ level, 2.1 mEq/L and 4.5 mEq/L, respectively). During hypokalemia, there was a shift of the stimulus-response curve to the right, a decrease in strength-duration time constant, a "fanning-out" of responses during threshold electrotonus, a reduction in relative refractory period, and an increase in superexcitability; all of these indicate axonal hyperpolarization, presumably due to the K+ equilibrium potential being more negative. These indices returned to normal 20 h later, associated with normalization of the serum K+ level. These results demonstrate that the changes associated with hypokalemic paralysis are not confined to muscle and that axons undergo hyperpolarization in vivo. Multiple excitability measurements can be used as a tool to identify changes in membrane potential of human axons.
KW - Hypokalemia
KW - Membrane potential
KW - Multiple excitability measurements
KW - Refractory period
KW - Superexcitability
KW - Threshold of electrotonus
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U2 - 10.1002/mus.10169
DO - 10.1002/mus.10169
M3 - Article
C2 - 12210395
AN - SCOPUS:0036339415
SN - 0148-639X
VL - 26
SP - 283
EP - 287
JO - Muscle and Nerve
JF - Muscle and Nerve
IS - 2
ER -