Differences in energy metabolism and neuromuscular transmission between 30-Hz and 100-Hz stimulation in rat skeletal muscle.
OBJECTIVE
To examine differences in energy metabolism and neuromuscular transmission failure in rat hindlimb muscles subjected to electric stimulation at different frequencies.


METHODS
Experimental animal study.


METHODS
Bioenergetic Research Center at Otsuka Pharmaceutical Company, Otsuka, Japan.


METHODS
Thirty-two 25-week-old male Wistar-Kyoto rats.


METHODS
With the rat under general anesthesia, the sciatic nerve was electrically stimulated at 30Hz and 100Hz to induce muscle contraction.


METHODS
Energy level and intracellular pH of muscles by phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS); M-wave amplitude of muscles by electromyography.


RESULTS
During the first 4 minutes under stimulation at 30Hz and at 100Hz, energy level and intracellular pH dropped to their lowest values (p <.05 or p <.01); the values then recovered with time. Recovery rates of energy level and intracellular pH during stimulation at 100Hz were greater than those observed during stimulation at 30Hz. The M-wave amplitude during 100-Hz stimulation was permanently and significantly lower than that measured during 30-Hz stimulation (p <.01), and the recovery rate of M-wave amplitude after stimulation at 100Hz was slower than that after stimulation at 30Hz.


CONCLUSIONS
Neuromuscular transmission failure was greater with 100-Hz stimulation than with 30-Hz stimulation. This finding may account for the rapid recovery of energy level and intracellular pH that occurs with stimulation at 100Hz.
Takata
S
S
Department of Orthopaedic Surgery, School of Medicine, University of Tokushima, Tokushima, Japan.
Ikata
T
T
D000818:Animals; D004558:Electric Stimulation; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology*; D010759:Phosphorus Isotopes; D005082:Physical Exertion / Q000502:physiology; D051381:Rats; D011921:Rats, Inbred WKY; D012584:Sciatic Nerve / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D010759:Phosphorus Isotopes