84 Pharmacology of Salivary Secretion 



the secretory effect of adrenaline and, particularly, of noradrenaline. 

 A similar, sensitizing effect is exerted by cocaine. If a suitable dose 

 of cocaine is injected through the salivary duct, it can be seen that 

 the secretory effect of parasympathetic and sympathetic stimulation 

 is abolished because of a local anaesthetic action, the effect of 

 injected acetylcholine is unchanged but the response to injected 

 noradrenaline increased. 



Among the sympathomimetic agents, tyramine is of particular 

 interest in this connection. It causes a secretion from the submaxil- 

 lary gland of the cat which decreases with repeated doses and which 

 is abolished by previous extirpation of the superior cervical gan- 

 glion; it is therefore assumed to act not directly on the receptors 

 of the gland cells but through some indirect mechanism (Strom- 

 blad, 1956). 



The sympathomimetic amines may also affect salivary secretion 

 through their action on the blood vessels. In Chapter VII the 

 inhibition of salivary secretion resulting from sympathetic vaso- 

 constriction will be discussed. Adrenaline, for instance, decreases 

 the flow of saliva produced by chorda stimulation, particularly if 

 the rate of secretion is high. It has been pointed out by Dirnhuber 

 and Evans (1954) that adrenaline may also cause anoxia and further 

 reduce a secretion in the gland because of its metabolic effect. 



SYMPATHOLYTIC AGENTS 



The early investigations on the actions of ergot by Dale (1906) 

 showed that this drug can abolish the secretory effects of adrenaline 

 and sympathetic stimulation on the submaxillary gland of the cat 

 while the effect of chorda stimulation is retained. The sympatho- 

 lytic effect on the salivary glands exerted by ergotamine was shown 

 by Yonkman (1933). Dibenamine, likewise, antagonizes the secre- 

 tory effect of sympathetic stimulation on the submaxillary gland ; 

 the effect of chorda stimulation may in addition be slightly reduced, 

 probably secondary to a fall in blood pressure (Uvnas, 1948). 



The motor effect of sympathetic stimulation on the salivary 

 glands is abolished by ergotamine (Babkin, 1929). The vasodilata- 

 tion, accompanying salivary secretion in response to sympathetic 

 stimulation, is abolished by agents which annul the secretion, as 

 discussed in Chapter VII. The sympathetic vasoconstriction is 

 often abolished too, for instance, by dihydroergotamine or antistin. 

 With some drugs, however, it is possible to separate constriction 



