1989 Volume 158 Issue 1 Pages 37-46
OKAYAMA, H., OKAYAMA, M., ISHII, M., SASAKI, H. and TAKISHIMA, T. Effect of Duration of Vagal Stimulation on Shortening Velocity of In Vivo Canine Trachealis Muscle. Tohoku J. Exp. Med., 1989, 158 (1), 37-46 - 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±105g/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.
