Nonlinear summation of contractions in striated muscle. I. Twitch potentiation in human muscle
Tóm tắt
The adductor pollicis of intact man was electrically stimulated via its motor nerve, with series of two supramaximal pulses delivered at various intervals. Muscle surface action potential, myogram and corresponding first derivative (dPt/dt) were recorded under isometric conditions. When two stimuli are delivered at intervals shorter than 150 ms a more-than-linear summation, or potentiation, is observed. This potentiation of force production by a second stimulus involves both increased duration and acceleration of contraction. The potentiation is larger in muscles with small twitch-to-tetanus ratio (Pt/Po), and is found to decrease or increase when Pt/Po is respectively augmented (for example in positive staircase and in contractile disuse) or reduced (for example in negative staircase and in dynamic training). No significant modification of muscle surface action potential is observed when these contractile changes are present. Combined prolongation and intensification of intracellular processes, associated with muscle excitation-contraction coupling in a twitch, could account for the potentiation observed in nonlinear summation of contractions.
Tài liệu tham khảo
Ambrogi-Lorenzi, C., Colomo, F. &Lombardi, V. (1983) Development of force-velocity relation, stiffness and isometric tension in frog single muscle fibres.J. Musc. Res. Cell Motility 4, 177–89.
Ashley, C. C. &Ridgway, E. B. (1970) On the relationship between membrane potential, calcium transient and tension in single barnacle muscle fibres.J. Physiol., Lond. 209,105–30.
Buller, A. J. &Lewis, D. M. (1965) The rate of tension development in isometric tetanic contractions of fast and slow skeletal muscles.J. Physiol., Lond. 176, 337–54.
Cecchi, G., Griffiths, P. J. &Taylor, S. (1982) Muscular contraction: Kinetics of crossbridge attachment studied by high-frequency stiffness measurements.Science, N. Y. 217, 70–2.
Close, R. (1972) Dynamic properties of mammalian skeletal muscles.Physiol. Rev. 52, 129–47.
Colomo, F. &Rocchi, P. (1965) Staircase effect and post-tetanic potentiation in frog nerve-single muscle fibre preparations.Arch. Fisiol. 64,189–266.
Cooper, S. &Eccles, J. C. (1930) The isometric responses of mammalian muscles.J. Physiol., Lond. 69, 377–85.
Desmedt, J. E. &Hainaut, K. (1968) Kinetics of myofilament activation in potentiated contraction: the staircase phenomenon in human skeletal muscle.Nature, Lond. 217, 529–32.
Duchateau, J. &Hainaut, K. (1984) Isometric or dynamic training: differential effects on mechanical properties of a human muscle.J. appl. Physiol.: Respirat. Environ. Exercise Physiol. 56, 296–301.
Duchateau, J. &Hainaut, K. (1986) Nonlinear summation of contractions in barnacle muscle fibres. II. Evidence of intensification of intracellular Ca2+ movement.J. Musc. Res. Cell Motility 7, 18–24.
Hainaut, K. &Desmedt, J. E. (1974a) Calcium ionophore A 23187 potentiates twitch and intracellular calcium release in single muscle fibres.Nature, Lond. 252, 407–8.
Hainaut, K. &Desmedt, J. E. (1974b) Effect of Dantrolene sodium on calcium movements in single muscle fibres.Nature, Lond. 252, 728–30.
Hill, A. V. (1949) Abrupt transition from rest to activity in muscle.Proc. R. Soc. Ser. B. 136, 399–420.
Huxley, A. F. (1974) Muscular contraction.J. Physiol., Lond. 243, 1–43.
Huxley, A. F. &Simmons, R. M. (1971) Proposed mechanism of force generation in striated muscle.Nature, Lond. 233, 533–8.
Mannard, A. &Stein, R. B. (1973) Determination of the frequency response of isometric soleus muscle in the cat using random nerve stimulation.J. Physiol., Lond. 229, 275–96.
Parmiggiani, F. &Stein, R. B. (1981) Nonlinear summation of contractions in cat muscles. II. Later facilitation and stiffness changes.J. gen. Physiol. 78, 295–311.
Podolsky, R. J. (1960) Kinetics of muscular contraction: the approach to the steady state.Nature, Lond. 188, 666–8.
Ranatunga, K. W. (1978) Characteristics of tension recruitment and mechanical activation in mammalian skeletal muscle.Expl Neurol. 61, 175–84.
Stein, R. B. &Parmiggiani, F. (1981) Nonlinear summation of contractions in cat muscles. I. Early depression.J. gen Physiol. 78, 277–93.
Takamori, M., Hazama, R. &Tsujihata, M. (1978) Active state properties of denerved and immobolized muscle: comparison with dystrophic muscle.Neurology 28, 603–8.