The "active state" during contracture of the frog's rectus / by W.D.M. Paton.

  • Paton, William D. M
Date:
[1957?]
Catalogue details

Licence: In copyright

Credit: The "active state" during contracture of the frog's rectus / by W.D.M. Paton. Source: Wellcome Collection.

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    [From the Proceedings of the Physiological Society, 26-27 April 1957.] Journal of Physiology, 137, 59-60 P. The ‘active state’ during contracture of the frog’s rectus. By W. D. M. Paton. Department of Pharmacology, Royal College of Surgeons Examination Hall, Queen Square, London, W.C. 1 It was noticed, during experiments on the frog’s rectus using the 'pendulum’ lever (Paton, 1957), that acetylcholine reduced the extensibility of the muscle. This suggested that acetylcholine produced in the muscle a state corresponding to the 'active state’ described by Hill (1949), during propagated responses in frog sartorius. The rectus was immersed in modified Ringer’s solution (NaCl, 6g; KC1, 0-15 g; CaCl2.6H20, 0-3 g; NaHC03, 0*5 g; water, 1000 ml.) bubbled with 5% C02/95 % 02. Its lower end was attached to the bottom of the 4 ml. bath which Load (g) 1-5 1-0- 0-5- 0- °1 5- 10* 15-* Extension (mm) Fig. 1. Frog’s rectus abdominis. Upper part of tracing: superimposed responses to acetylcholine 10-6 recorded (a) as a continuous contraction, (b) as tension developed to repeated stretch from a state of zero tension. Lower part of tracing: record of movement of the bath, by which the muscle was stretched either (a) continuously, or (b) intermittently. The actual extension of the muscle is less than that shown by this record, by 1/8*5 x the excursion of the pendulum lever. Minutes 4._Xmmm, I_L_| t Acetylcholine 10 -6 Wash was carried on a calibrated rack and pinion, thus allowing the muscle to be stretched. Its upper end was attached to a pendulum lever, magnification 8-5, load 500 mg/cm deflexion on the smoked drum. Fig. 1 contrasts the effects of acetylcholine (a) recorded as a continuous contraction, and (6) recorded in response to repeated brief extensions. Two differences appear: (1) the onset and offset of action are much quicker when detected by response to stretch; (2) the stretch experiment reveals a peak and subsequent decline, which are obscured with the conventional method. [P. T. O.