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.

  • William Paton
Date:
[1951?]
Catalogue details

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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    °f 60 Mg*/kg- which depresses the tibialis twitch by 40-70 % will affect the respiratory movements to an equal degree, and the characteristic difference observed in chloralose anaesthesia between the actions of decamethonium on tibialis twitch and on respiratory movements is less pronounced. The augmentation of respiratory movements observed occasionally after small doses of decamethonium in cats under chloralose was never seen under ether anaesthesia. This corresponds to our previous observation that under ether the potentiation of the muscle twitch does not occur. Fig. 3 illustrates the abolition by ether of the potentiation of the twitch of tibialis due to de¬ camethonium, together with the diminution of its paralysing action. In this experiment, the twitches of the tibialis were recorded simultaneously with those of the soleus muscle. The stimulating action of decamethonium on this latter muscle is more pronounced than on the tibialis, but again it is abolished by ether. N hereas in ether anaesthesia, the threshold dose of decamethonium for affecting the tibialis was raised, the reverse was true for D-tubocurarine (Table 1). Paralysis of the tibialis twitch was obtained with a dose of d- tubocurarine approximately 30 % less than that required in cats anaesthetized with chloralose. In addition, D-tubocurarine also became more active in depressing respiration; the threshold dose required to do this was reduced to 0-04 mg./kg., about half that required in chloralose anaesthesia. Even under ether anaesthesia, therefore, decamethonium still affects the respiration relatively less than does D-tubocurarine. A . • • 7 Unanaesthetized animals Actions m monkeys A comparison was made, for both drugs, of the dose required to cause general muscular weakness with that required to produce impairment of respiratory movements. The muscular weakness was assessed in monkeys by their inability to sit up or to support their heads or arms, and by infrequency and weakness of spontaneous movements. In each experiment the time required for complete recovery from paralysis was determined. In assessing impairment of respiratory movements, depression of the respiration so far as to necessitate artificial respiration was chosen as a convenient reference point. The results of repeated tests on six monkeys are given in Table 2. The injection of 0-5-0-77 mg./kg. decamethonium caused general motor paralysis lasting 55-130 min. Artificial respiration was needed in only 17% of the animals receiving 0-5 mg./kg. and in 80% of those receiving 0-77 mg./kg. decamethonium iodide. On the other hand, 0-15 mg./kg. of D-tubocurarine necessitated artificial respiration in all the animals tested, although recovery of motor paralysis was complete in 30 min. The predilection of D-tubocurarine for respiratory effects in the monkey was particularly striking with small doses; even 0-075 mg./kg. caused exaggerated movements of the nostrils and thorax
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