86 Pharmacology of Salivary Secretion 



compatible with the fact that it increases the effect of chorda 

 stimulation but not that of pilocarpine and with the statement in 

 the early literature that atropine abolishes the secretion caused by 

 mercury salts. 



Histamine. Dale and Laidlaw (1910) found that histamine causes 

 secretion of saliva in cats and dogs. This effect has been studied by 

 many later investigators; the result of this work has been sum- 

 marized by Babkin (1950). Generally it may be said that fairly big 

 doses of the drug are required to cause a slight secretion of saliva, 

 compared with those eliciting a fall in blood pressure, contraction 

 of plain muscle and secretion of gastric juice. Several different 

 mechanisms may be at work. The central effects of histamine have 

 already been mentioned. The ability of histamine to release adren- 

 aline should perhaps also be kept in mind. In addition, histamine 

 has apparently a double peripheral effect. It contracts those ele- 

 ments which expel saliva from the glands and it has a true secretory 

 effect on the gland cells. The latter, but not the former, action is 

 abolished by atropine. Dale and Laidlaw described the secretory 

 effect as being of the pilocarpine type and pointed out that both 

 agents possess an imidazole ring; it may be added that another 

 imidazole derivative, naphazoline (privine), has been found to have 

 a slight secretory effect, which is abolished by atropine (Yonkman, 

 Rennick and Schwerma, 1945). 



Nitrogen mustards. Investigations during the last war, only in 

 part published in the open literature, disclosed that protracted 

 salivation is a prominent symptom after lethal doses of nitrogen 

 mustards. The peculiar type of secretory response obtained after 

 an injection of meihyl-bis (2-chloroethyl) amine (HN2) into the 

 carotid artery of cats have been described by Hunt and Philips 

 (1949), who have also quoted earlier investigations in this field. 

 Shortly after the injection of the drug saliva starts to flow from the 

 submaxillary gland. The secretion soon ceases and during a period 

 of about five minutes there is no flow. Salivation is then resumed 

 and gradually attains a maximal rate at which it continues for 

 hours. When atropine is administered before the HN2, salivation 

 is prevented. However, if atropine is given after the initial appear- 

 ance of salivation, even as early as in the interim between the two 

 phases of salivation, it fails to alter the delayed response. 



As to the mechanism responsible for the secretion the following 

 observations have been made. Nitrogen mustards cause a pro- 



