title: Quantitative analysis of muscle hardness in tetanic contractions induced by electrical stimulation in rats.
abstract: The purpose of this study was to investigate the in vivo relation between muscle hardness during an electrically induced contracting state and neuromuscular functions (M-wave and developed tension). Sixteen Sprague-Dawley rats were deeply anesthetized with urethane. Muscle hardness was measured quantitatively at the mid-portion of the gastrocnemius (GS) muscle during tetanic contractions induced by electrical stimulation (50 Hz, 100 micros duration) of the sciatic nerve or of the muscle directly. The M-wave was recorded with a pair of wire electrodes inserted into the muscle, and the developed tension was monitored with a push-pull gauge. Muscle hardness, M-wave amplitude and developed tension increased rapidly with the onset of nerve stimulation. Similar but intensity-dependent increases in muscle hardness and tension were observed following direct tetanic stimulation of the muscle. The hardness measured during nerve stimulation was correlated with the amplitude of the M-wave (r = 0.62, P < 0.0001) and the developed tension (r = 0.85, P < 0.0001). These phenomena were suppressed by pancuronium treatment (2 mg/ml, i.v.). These results suggest that muscle tension might be the most important factor for transcutaneously measured muscle hardness induced by tetanic muscle contraction.
authors.affiliation: Department of Physiology, Meiji University of Oriental Medicine, Nantan-city, Kyoto 629-0392, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Morisada
authors.forename: Kaoru
authors.initials: K
authors.lastname: Okada
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawakita
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D006244:Hardness; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D010197:Pancuronium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology
chemical_list: D010197:Pancuronium