The pharmacology of decamethonium / by W.D.M. Paton.

  • Paton, William D. M.
Date:
[1951?]
Catalogue details

Licence: In copyright

Credit: The pharmacology of decamethonium / by W.D.M. Paton. Source: Wellcome Collection.

    13/16 (page 359)
    Discussion of the Paper Doctor George Acheson (University of Cincinnati College of Medicine, Cincinnati, Ohio): I heartily agree with Doctor Paton’s insistence on sound terminology. We need clear words for the clearer analysis and understand¬ ing of the mechanisms we study. I would quibble with the term “threshold to acetylcholine,” since I believe Doctor Paton is considering the action of acetylcholine by depolarization of the end plate. He is not dealing pri¬ marily with an all-or-none effect, and I believe that the term “threshold” should be reserved for all-or-none stimulation. The threshold is like the doorstep: either you step up or you don’t step up. The acetylcholine effect on the transmission mechanism is a graded phenomenon. I would say that what he was talking about was the sensitivity of the end-plate mechanism to acetylcholine in graded terms. In order to get twitches from muscles, you have to give acetylcholine rapidly into an artery very close to the muscle, in such a way that it gets swept in very rapidly and hence depolarizes very rapidly. If you give it at a greater distance, you get no twitches, presumably because the depolariza¬ tion occurs slowly. Now, you get the same difference in the application of electric current to a conducting structure. In order to get a conducted response, you must apply a certain difference of potential very abruptly. If you apply it more gradually, no response occurs. The latter is attributed to a process called “accommodation.” If the end-plate depolarization ex¬ cites the conducting system of the muscle by a mechanism similar to that occurring under a stimulating electrode, its behavior should follow similar laws. Doctor J. L. Lilienthal (The Johns Hopkins Hospital, Baltimore, Maryland): Everyone working in this field is in Doctor Paton’s debt for a large amount of beautifully conceived and cleanly executed experimental work which has illuminated several facets of the general problem. With much of his stimulating analysis, there will exist general agreement. There are, however, certain observations already described which suggest that the time, although always ripe for hypothesis, is perhaps not yet here for too rigid a classification. Some of the differences in phenomena described by Doctor Jarcho and by Doctor Paton might be attributed to differences in the species studied. If this be the case then one is confronted with the dilemma: is it the cat or the rat which represents the exception? I am sure I do not know, but it may place this question in a different light if I remind you that those who work with primates, human or sub-human, might consider both cat and rat to be distinctly second-class citizens in this hierarchy. It is always tempting to make observations on the tibialis muscle of the cat, then construct from these observations hypotheses applicable to all cat muscle, and finally to generalize about muscle in general. This natural series of steps is valuable only when we keep clearly in mind that such generalizations may later require considerable qualifica¬ tion in the light of observations on other forms of muscle.