The action of D-tubocurarine and of decamethonium on respiratory and other muscles in the cat / by W.D.M. Paton and Eleanor J. Zaimis.

  • Paton, William D. M.
Date:
[1951?]
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Licence: In copyright

Credit: The action of D-tubocurarine and of decamethonium on respiratory and other muscles in the cat / by W.D.M. Paton and Eleanor J. Zaimis. Source: Wellcome Collection.

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    [Reprinted from the Journal of Physiology, 1951, Vol. 112, Nos. 3 and 4, p. 311.] PRINTED IN GREAT BRITAIN J. Physiol. (1951) 112, 311-331 THE ACTION OF d-TUBOCURARINE AND OF DECAMETHONIUM ON RESPIRATORY AND OTHER MUSCLES IN THE CAT By W. D. M. PATON and ELEANOR J. ZAIMIS* From the National Institute for Medical Research, Mill Hill, London, N.W. 7 (Received 22 March 1950) In a previous paper (Paton & Zaimis, 19495) we have referred to the way in which decamethonium and D-tubocurarine chloride, when administered intra¬ venously to the cat anaesthetized with chloralose, differed considerably in the readiness with which they depressed the activity of the respiratory muscles relative to that of the limb muscles. This difference has been further studied in the experiments now described, of which a brief account has already appeared (Paton & Zaimis, 1949 a). The mode of action of decamethonium has recently been further analysed (Brown, Paton & Vianna Dias, 1949; Burns, Paton & Yianna Dias, 1949; Zaimis, 1949; Buttle & Zaimis, 1949). We may conclude that the main difference between decamethonium and D-tubocurarine is the following. D-Tubocurarine paralyses neuromuscular conduction by rendering the end-plate less sensitive to the depolarizing action of acetylcholine. Decamethonium, however, like acetylcholine, depolarizes the end-plate region, and may, like acetylcholine, according to the circumstances either initiate a propagated contraction in the muscle, or give rise to neuromuscular block. Decamethonium should thus be compared with acetylcholine rather than with curare in its mode of action. This fundamental distinction from curare needs to be borne in mind in considering the differences, described below, between the two drugs. METHODS Cats anaesthetized with chloralose (80 mg./kg.), after induction by ether, were used in most j experiments. Twitches and tetani of the soleus and tibialis muscles were excited by maximal j shocks applied to the tied sciatic nerve in the thigh. The contractions of these muscles were applied ** to a flat spring myograph and recorded on a smoked drum. In some experiments records of the j mechanical response of the two muscles in the same leg were recorded on the same drum. 1 * j Present address: Pharmacology Department, School of Pharmacy, 17 Bloomsbury Square, j London, W.C. 1. I