76 Pharmacology of Salivary Secretion 



salivation, retching, vomiting and other symptoms. The drugs 

 were assumed to act by direct stimulation of hypothalamic nuclei 

 after diffusion through the ependymal lining of the third ventricle, 

 and the observations were taken as evidence to show the existence 

 of a "parasympathetic centre" in the diencephalon. Some salivary 

 secretion was described by Henderson and Wilson (1936) to occur 

 after intraventricular injection of acetylcholine in man; it was com- 

 bined with nausea. In experiments on monkeys, however, no 

 secretory effects of pituitrin or acetylcholine given into the lateral 

 ventricles were observed; pilocarpine caused secretion (Light and 

 Bysshe, 1933). In rabbits pilocarpine was likewise found to cause 

 a secretion of saliva when injected intraventricular^ (Light, Bishop 

 and Kendall, 1933). Aird and Montgomery (1936) found pilo- 

 carpine given into a lateral ventricle of dogs to act even on a 

 denervated salivary gland and concluded that the drug exerted its 

 effect after absorption into the blood. This is obviously an import- 

 ant source of error, necessary to take into account in experiments 

 of this type, when the drugs have a peripheral, secretory effect. In 

 the case of pituitrin no such site of action seems to exist. 



Among the effects of central excitation caused by curare saliva- 

 tion has been described. McGuigan (19 16) observed a flow of saliva 

 in dogs after injection of curare into the fourth ventricle. Salama 

 and Wright (1950) saw a secretory effect in cats when d-tubocura- 

 rine had been injected into a lateral ventricle and regarded this 

 experiment as support for the view expressed by Mclntyre (1947), 

 according to which salivation occurring after rapid intravenous 

 injection of curare is of central origin; it is associated with retching 

 and often with vomiting. 



In their chronic experiments on unanaesthetized cats, Feldberg 

 and Sherwood have found salivation to occur after the injection 

 into the lateral ventricle of doses of ^-tubocurarine as small as 

 30 jag. Flow of saliva and defaecation appear as initial symptoms 

 in a syndrome characterized by convulsions and electrical changes 

 in the brain resembling those of grand mal epilepsy (Feldberg and 

 Sherwood, 1954; Feldberg, 1957). Various other drugs applied in 

 the same way, histamine, 5-hydroxytryptamine, hexamethonium, 

 decamethonium, banthine and atropine were also found to cause 

 a profuse secretion of saliva. It is interesting to observe that these 

 drugs all caused tachypnoea with or without panting; most of 

 them caused retching and vomiting as well. 



