Effect of duration of vagal stimulation on shortening velocity of in vivo canine trachealis muscle.
We studied shortening velocity of in vivo canine trachealis muscle contracted by bilateral vagus nerve stimulation, as a function of duration of contraction. The cervical trachea was transected at two locations, cut at the ventral portion, and opened. One side of the cartilage cut was connected to a force transducer and the other to a lever with a given weight as an afterload, the length of which was measured by a linear displacement transducer. Bilateral vagosympathetic trunks were stimulated by supramaximal electrical impulses. With vagal stimulation, the trachealis muscle started to contract isometrically and at a given time the muscle was allowed to contract isotonically by unlocking a stopper at a given afterload. The shortening velocity was reduced with longer duration of active state. Ten sec after vagal stimulation the maximum force was 730 +/- 105 g/cm2 (mean +/- S.D.) and maximum velocity at zero load calculated by Hill's equation was 0.092 l0/sec. We conclude that the force-velocity relationship of in vivo canine trachealis muscle stimulated by vagus nerves exhibits a time-dependency similar to that in vitro.
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai.
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H
Okayama
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Okayama
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M
Ishii
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Sasaki
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Takishima
D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D007700:Kinetics; D009119:Muscle Contraction; D009132:Muscles / Q000294:innervation / Q000502:physiology*; D013997:Time Factors; D014630:Vagus Nerve / Q000502:physiology*