The paralysis of autonomic ganglia, with special reference to the therapeutic effects of ganglion-blocking drugs / by W.D.M. Paton.

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

Licence: In copyright

Credit: The paralysis of autonomic ganglia, with special reference to the therapeutic effects of ganglion-blocking drugs / by W.D.M. Paton. Source: Wellcome Collection.

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    delicate nerve terminals, is attacked. This is tested by perfusing the ganglion and determining whether the re¬ lease of acetylcholine by excitation of the pre-ganglionic nerve persists in the presence of hexamethonium. Even with the injection of a large dose of hexamethonium exclusively into the ganglion perfusion system, acetyl¬ choline is still normally released. Finally, it was ob¬ served that the ganglion was not depolarized during the action of hexamethonium and that the paralysis was never preceded by excitation (Paton and Perry, 1951). Effects on the Blood Pressure The effects of hexamethonium on the cat’s blood pressure are of particular interest, with reference to its use in hypertension. A dose of 1-2 mg./kg. usually produces a moderate fall of blood pressure ; but further doses, up to 20-30 mg./kg., produce no further effect. At the same time, the effects of nicotine (a stimulant to the vasomotor ganglia) are abolished, but the effects of acetylcholine and adrenaline are not reduced. Such an experiment (which could equally well be done in man) shows: (1) that the actions of hexamethonium on the blood pressure are exerted only by the release of autonomic tone, and not by any direct vascular action ; (2) that it has no other depressor effect even in large doses ; and (3) that it has no atropine-like or “ adreno¬ lytic ” action. The actions of acetylcholine and adrenaline are, how¬ ever, altered. The depressor effect of acetylcholine is prolonged (although hexamethonium is free of anti¬ cholinesterase activity); and the pressor effect of adrena¬ line is both increased and prolonged. These effects are no doubt due to the paralysis of the compensating mechanisms normally maintaining the constancy of the blood pressure. Similar observations have been made with tetraethylammonium (Page and Taylor, 1947). When using ganglion-blocking agents, therefore, it is necessary to remember that the response to drugs and procedures affecting the blood pressure will necessarily be exaggerated, as the mechanisms maintaining a normal blood pressure are weakened. The pharmacological study of hexamethonium, in short, has shown it to be a specific ganglion-blocking agent of low toxicity, and to be free from other pro¬ perties such as stimulation of nerve terminations, ganglia, striated muscle or smooth muscle, neuro¬ muscular blocking action, atropine-like action, histamine i