Parasympathomimetic Drugs 79 



The ordinary vascular effect of acetylcholine in the salivary 

 glands is a vasodilatation. According to Hilton and Lewis (1955a 

 and b) this dilatation is functionally secondary to the effect on the 

 gland cells and is caused by bradykinin. In this respect the dilata- 

 tion resembles that caused by stimulation of the parasympathetic 

 fibres ; but it differs in being completely abolished by atropine. It 

 is not known whether acetylcholine in addition has a "direct" 

 vasodilator effect on the smooth muscles of the gland vessels. 



The effects of acetylcholine and other secretory agents can also be 

 demonstrated by an increased uptake of oxygen in vitro (Deutsch 

 and Raper, 1938; Stromblad, 1957a). 



Acetylcholine given intravenously has been shown to evoke a 

 secretion of saliva in man (Weiss and Ellis, 1934; Kern and Almy, 

 1952). For use in human beings, however, methacholine seems 

 preferable and it has been given by numerous investigators (Starr, 

 Elsom and Reisinger, 1933 ; Weiss and Ellis, 1934; Kern and Almy, 

 1952; Thaysen, Thorn and Schwartz, 1954; Diamant, Diamant 

 and Holmstedt, 1957). Dameshek and Feinsilver (1937) suggested 

 that mecholyl should be used as a diagnostic test in patients sus- 

 pected of having a poisoning due to belladonna alkaloids; the 

 failure of appearance of salivation and other characteristic effects 

 would speak in favour of such a diagnosis. Pilocarpine has, like- 

 wise, been given to human beings to evoke secretion of saliva, for 

 instance, by Marshall (1904), Nyman (1942). Necheles and Levit- 

 sky (1936-37) injected a standard dose of pilocarpine subcutane- 

 ously and found it to cause a smaller response from the salivary 

 glands in peptic ulcer patients than in normal subjects. 



It is not possible, within a limited space, even to enumerate more 

 than a small number of all the drugs possessing a parasympatho- 

 mimetic action on the salivary glands. Mention has already been 

 made of tetramethylammonium which causes a profuse secretion 

 abolished by atropine (Burn and Dale, 191 5). When y-crotonic 

 betaine, a pharmacologically relatively inert substance present in 

 animal tissues, is converted into the methyl ester, a substance 

 causing profuse and prolonged salivation is obtained (Burgen and 

 Hobbiger, 1949). Bicarnesine, another betaine derivative, has also 

 a secretory effect (Charlier, 1956). The effects of these various 

 drugs would be classified as "muscarinic" ; it is therefore gratifying 

 to learn that even chromatographically pure, crystalline muscarine, 

 prepared from Amanita muscaria, evokes a flow of saliva (Fraser, 



