92 



Drs. P. W. Mott and W. D. Halliburton. 



Physiological Action of Choline. 



The doses employed were from 1 to 10 c.c. of a 0*2 per cent, solution, 

 either of choline or of its hydrochloride. These were injected intra- 

 venously. 



The fall of blood pressure is in some measure due to its action on 

 the heart, but is mainly produced by dilatation of the peripheral vessels, 

 especially in the intestinal area. This was dmonstrated by the use of 

 an intestinal oncometer. The limbs and kidneys are somewhat lessened 

 in volume ; this appears to be a passive effect, secondary to the fall in 

 general blood pressure. The drug causes a marked contraction of the 

 spleen, followed by an exaggeration, of the normal curves, due to the 

 alternate systole and diastole of that organ. 



The action on the splanchnic vessels is due to the direct action of the 

 base on the neuro-muscular mechanism of the blood vessels themselves ; 

 for after the influence of the central nervous system has been removed 

 by section of the spinal cord, or of the splanchnic nerves, choline still 

 causes the typical fall of blood pressure. The action of peripheral 

 ganglia was in other experiments excluded by poisoning the animal 

 previously with nicotine. 



Section of the vagi produces no effect on the results of injecting 

 choline. 



We have obtained no evidence of any direct action of the base on 

 the cerebral vessels. 



Choline has little or no action on nerve trunks, as tested by their 

 electrical response to stimulation. This aspect of the subject has been 

 taken up by Dr. Waller and Miss Sowton, who will publish their 

 results fully in a separate paper. 



Choline has no effect on respiration. 



The effect of choline soon passes off, and the blood pressure returns 

 to its previous level. This is due partly to the great dilution of the 

 substance injected by the whole volume of the blood, and may be 

 partly due to the excretion of the alkaloid, or to its being broken up 

 into simpler substances by metabolic processes. We could not find it 

 in the urine. 



If the animal has been previously anaesthetised with a mixture of 

 morphine and atropine, the effect produced by choline is a rise of 

 arterial pressure, accompanied by a rise of the lever of the intestinal 

 oncometer. Other anaesthetics cause no change in the usual results. 

 We consider this observation of some importance, for it shows how the 

 action of one poison may be modified by the presence of another. 

 This has some bearing on General Paralysis, for the arterial tension in 

 that disease is usually high, not low, as it would be if choline were the 

 only toxic agent at work. 



