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.

    7/10 (page 65)
    65 ■“ * Third, we have a difference m the localization of the cholinesterases which at t^r*0 T SMng there at the post«- membrane aitmg foi the acetylcholine, whereas in the ganglion it seems to exist mostly presynaptic terminals themselves from where the acetylcholine has just come. Obviously it is much more likely to modify the postsynaptic effects of the ug m the former case and, correspondingly, anticholinesterases will there have m°re vlSor°us action. Indeed at the ganglion it is not impossible that diffuZn p ys an appreciable part in removing acetylcholine from the immediate site of ??i i0ne ai?P 16S,a dlffusion equation one can calculate that 90 per cent of the acetjdchohne released at a point source could have diffused away\om a cute -M x 2fi x 2M round that source, within 1.2 msec., a sufficiently short period to conform to the facts of transmission. P Fourthly, one might suggest that there is also an anatomical basis for the lesistance to cathodal block. In the analysis of the action of depolarizing agents t e endplate, the onset of inexorability appeared to be closely associated^vith the spread of the depolarization into the adjacent muscle fibre. Now this is at the endplate region, a relatively easy process, since the endplate is a small depolarized cTrrentTuldtheTf °f *Mvdy wide reser™r; a considerable bL but the elef°re be expected t0 flow‘ At the ganglion, however, the sink is big, but the reservoir is very narrow and extended. And it may well be that there so rapidly.CUrrent Cann0t be S° great and henCe the inexeitability cannot develop We reach therefore, the following final position. Although ganglionic and muromuscuiar transmission have many striking similarities, there are also some P tant differences. But these differences, on examination, and on comparing lSe“nTransm ^ SynapSe\may WeU arise- not from ^ fundamental ence m transmission processes, but as consequences of the varying anatomy 1g,,a8e of “h ,y,“p“ “ “» ““m »iy by mZHoJZZ Tr F™m th“ 01 *“ly“ *h' obviously )IIows that at a central nervous synapse, there should be observed those features lese differ th1”10” k gangll0ni0 and neuromuscular synapse, and that where mera W hT b° a cosr resemblance to the ganglion. Such a harmless v erahzation has no tactical value, but might have some strategic use For ,uMnhave oW° J 5°, ^ that dmgS a°ting °n °entral nervous structures u d have one of at least five actions, in relation to a hypothetical transmitter- »at is they might imitate it, compete with it, (or have both these actions in ies), inactivate the enzyme destroying it, sensitize to it by some non-enzymatie eans or prevent the release of the transmitter. This is not, heuristically, a very mroachto thT’ but at leaSt h may prevent an over-simple oa h to the problem. A second point to be borne in mind is that there is no