82 Pharmacology of Salivary Secretion 



Numerous substitutes for atropine are available, some even more 

 potent in parasympatholytic action or even more long-acting than 

 atropine, some lacking the disadvantages discussed above. Scopol- 

 amine blocks secretion of saliva more strongly than atropine. 

 N-methylation of atropine or scopolamine further increases the 

 blocking effect. Methylscopolamine, for instance, blocks secretion 

 of saliva, induced by pilocarpine in man, very effectively (Nyman, 

 1943). Judging from sensitization experiments the tendency to in- 

 creasing tolerance is much less with this drug than with atropine 

 (Emmelin, i960). The same is true for the synthetic drug Ho-9980 

 (piperidinoethyldiphenylacetamide), the parasympatholytic pro- 

 perties of which were first investigated by Schaumann and Lindner 

 (195 1 ). This agent very strongly and specifically antagonizes the 

 effect on the salivary glands of parasympathetic stimulation (Em- 

 melin and Henriksson, 1953; Emmelin and Stromblad, 1957). A 

 great number of benzilic esters of alkamines have been studied as 

 atropine substitutes by Ing, Dawes and Wajda (1945); the pro- 

 nounced antisecretory actions of some of them have been investi- 

 gated by Bulbring and Dawes (1945). Another potent inhibitor of 

 salivary secretion is dibutoline (dimethyl-ethyl-/?-hydroxyethyl- 

 ammonium sulphate di-w-butyl-carbamate), studied by Feather- 

 stone and White (1945), Peterson and Peterson (1945) and Biggins 



(1948). 



Many drugs used therapeutically for various purposes produce 

 a dry mouth as a side-effect because of a more or less pronounced 

 parasympatholytic action. This is true of M ethanthelin and related 

 substances (Zupko and Prokop, 1954) and many of the antihist- 

 amines, for instance, diphenhydramine (see Anderson and Em- 

 melin, 1947). In therapeutic doses such agents may depress salivary 

 secretion because of this peripheral action and through a general 

 sedative and an antiemetic effect. Barbiturates may likewise inter- 

 fere with the secretion of saliva by several different actions (Stav- 

 raky, 1931; Montgomery, 1935; Emmelin, 1941; Brahammar and 

 Emmelin, 1941 ; Guimarais, Malafaya-Baptista, Garrett and Oss- 

 wald, 1955). For instance, in a cat, anaesthetized with hexobar- 

 bitone, there is no flow of saliva, and the secretory response to 

 sympathetic or parasympathetic stimulation or injected acetyl- 

 choline may be greatly reduced, whereas the response to adrenaline 

 is unaffected. 



