66 Innervation of the Glandular Elements 



THE AFFERENT NERVES OF THE SALIVARY GLANDS 



Various observations indicate that the salivary glands have a 

 supply of fibres carrying pain impulses. Claude Bernard (1858) 

 observed that direct stimulation of the submaxillary gland of a 

 non-anaesthetized dog caused evidence of pain. It is well known 

 that swelling of the gland is painful. When the salivary duct is 

 obstructed secretion of saliva during meals produces pain rn the 

 gland. Similarly, pain is experienced when fluid is injected through 

 the duct towards the gland to elicit secretion (Emmelin and Strom- 

 blad, 1954). An interesting phenomenon has been described by 

 Gardner and Abdullah (1955). In patients in which the superior 

 cervical ganglion had been excised, pain appeared in the parotid 

 region on eating. It was first seen during the second week after the 

 operation; it occurred just at the beginning of the meal and re- 

 mained for a few seconds. Sometimes it became milder over a 

 period of some months, but did not disappear. It was described 

 as similar to the pain experienced in mumps and was therefore 

 supposed to be the result of sudden increase in intracapsular ten- 

 sion occurring as a reflex response to the gustatory stimulus. Since 

 it was not abolished by atropine it could not be due to a sudden 

 production of saliva. Instead, an excessive vasodilatation was 

 thought to be the cause of the pain ; as atropine does not antagonize 

 the reflex vascular response but only the secretion it would not be 

 expected to have any effect. After a ganglionic blocking agent, or 

 after section of the glossopharyngeal nerve, no pain was obtained 

 on eating. The authors' explanation is that the pain arises because 

 on eating a vasodilation is elicited, which becomes abnormally big 

 when not antagonized by the sympathetic nerves ; since patients in 

 which the preganglionic sympathetic had been cut did not show the 

 phenomenon it was assumed that the decentralized postganglionic 

 sympathetic neurone was able to hold within physiological bounds 

 the vasodilatation on eating. 



A related phenomenon is probably the pain sometimes experi- 

 enced at meal times by hypertensive patients receiving bretylium. 



The hypothesis has been put forward that the chorda tympani 

 contains afferent fibres which transmit interoceptive impulses aris- 

 ing in the secreting gland to regions in the central nervous system, 

 from which the secretory activity can be modified (Galperin, 1936). 



