Transmission and block in autonomic ganglia / by W.D.M. Paton.

  • Paton, William D. M.
Date:
[1954?]
Catalogue details

Licence: In copyright

Credit: Transmission and block in autonomic ganglia / by W.D.M. Paton. Source: Wellcome Collection.

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    Reprinted from Pharmacological Reviews Vol. 6, No. 2, March, 1954 Printed in U.S.A. TRANSMISSION AND BLOCK IN AUTONOMIC GANGLIA W. D. M. PATON University College and University College Hospital Medical School, London, England The modern conception of transmission in the autonomic ganglion as being- mediated by a specific chemical substance, acetylcholine, derived in its earlier stages from experiments in which a close analogy was drawn or implied between the ganglion and the nerve muscle preparation. Thus Langley used a single druo- nicotine—to map out ganglia and to study the muscle receptor substance • and as early as 1914, Dale remarked on “the biochemical similarity between the I' §angllon cells of the whole involuntary system and the terminations of voluntary nerve fibres m striated muscle” (10). A review of the advances in our knowledge since those early experiments is a task better suited for a military historian than for a contributor to. this Symposium. But it is still of interest to go back to this ; oiiginal analogy and to ask how far, in the light of our newer knowledge, the two synapses can still be regarded as closely analogous. The point of this question is sharpened if one looks at the histological structures involved. The usual diagrammatic representation of a motor endplate is already over-simplified, but the usual diagram of a ganglionic synapse is an almost ri- ; diculous idealisation of the true state of affairs. To a naive observer it would seem nearly incredible that there should be many or even a few features in common betv een the compact motor endplate activating a muscle fibre, and the elaborate basket-work of fibrils which shrouds a neurone specialised to transmit signals | and to release at its far end a neuro-humor. We can conveniently begin, therefore, by discussing first those characteristics of transmission which are common to the two synapses, and then the differences between them. | Characteristics Shared by Neuromuscular and Ganglionic Synapses. At both sites acetylcholine produces a non-propagated depolarization of the receptor membrane. It had, of course, been well established during the anni mirabiles of chemical transmission from 1934 onwards that acetylcholine could stimulate both muscle and ganglion cell; and depolarization by acetylcholine of the motor end- ^plate has also been known for a considerable time for the frog (19), although only directly demonstrated for the mammal quite recently (5). Definite evidence has now been obtained that a comparable state of affairs exists at the ganglion (22). It could not lightly be assumed that this would be the case, in view of Gaskell’s (15) old observation (recently reinvestigated and confirmed by Burgen and Terroux (4)) that acetylcholine can increase the membrane potential of the auricle. At both sites it also appears that acetylcholine in producing its depolarization does so by some process which can be described as producing a “short circuit” of the imiting membrane (normally of a high specific resistance). This was demonstrated inequivocally in Fatt and Katz’s elegant experiments (13) on the motor end- Dlate, and they were even able to quantitate the change in resistance produced