516 PHARMACOLOGICAL ACTION OF TETRA-ALKYL-AMMONIUM COMPOUNDS. 



show that the effect is mainly peripheral. None of the other substances produced 

 this action, and no cause for the difference has been found. In anaesthetised rabbits 

 and cats these compounds cause a fall of blood-pressure sometimes preceded by a 

 slight initial rise. The fall of blood-pressure after the administration of tetra-methyl- 

 ammonium chloride is mainly vascular in origin, and, since it is associated with 

 diminished irritability of the splanchnic nerves, is probably due, considering the slight 

 effect of small concentrations of this substance on contractile tissue, to a depression 

 of the nerve-endings in the blood-vessels. The fall of blood-pressure produced by 

 the other members of the series has doubtless a similar cause. A rise of blood- 

 pressure may, however, be produced by these substances. Usually it is slight and 

 transient and precedes the fall, but on rare occasions with tetra-methyl-ammonium 

 chloride it has been marked and prolonged. In decerebrate animals a temporary fall 

 may be followed by a decided rise of blood-pressure, an effect which also occurs after 

 tri-methyl-ammonium chloride. The cause of the rise of blood-pressure has not been 

 investigated, but in view of the facts that doses of tetra-methyl-ammonium chloride 

 inducing this action stimulate the respiratory centre in decerebrate animals, and that 

 the fall of blood-pressure had been shown to be due to a peripheral cause, it was 

 attributed to stimulation of the vaso-motor centre. Later experiments, however, 

 suggest a peripheral influence, and further work on the subject is necessary. 



It is of interest to note that the paralysing action of these alkyl ammonium 

 compounds and their influence in reducing the blood-pressure of anaesthetised rabbits 

 are of the same order, but whether this is more than a casual connection has not been 

 determined. 



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