CHAPTER VI 

 EFFECTS OF DENERVATION 



Complete denervation affects the salivary glands seriously. Some 

 glands, it is true, which are endowed with the ability of sponta- 

 neous activity, continue to secrete at a slow rate just as they did 

 with the nerves intact ; shortly after postganglionic parasympathe- 

 tic denervation a transient secretion of peculiar, "paroxysmal" type 

 may be observed and under exceptional conditions some of the 

 denervated glands may show a "paralytic secretion". But with 

 these exceptions the denervated glands do not discharge any 

 saliva. In all glands the ability to adapt the activity to the 

 functional requirements is lost, for there is no hormonal control 

 mechanism left, as in the denervated pancreas, for instance ; and 

 there is no evidence to show that there are local reflexes, as in 

 the lower part of the alimentary canal, through which the struc- 

 tures can be activated after section of the extrinsic nerves. Function 

 is, in fact, usually as impaired in the salivary glands as in skeletal 

 muscles after denervation. As in skeletal muscle an atrophy occurs 

 with marked histological changes and a pronounced supersensitiv- 

 ity to chemical stimuli develops. The chemical composition of the 

 glands is affected; particularly changes in the activity of certain 

 enzymes have been investigated, in connection with studies of 

 the mechanism of the supersensitivity. 



The fact that the parasympathetic nerve supply of the salivary 

 glands is much more important than the sympathetic supply is 

 apparent from denervation experiments. Structural and functional 

 changes are particularly serious after section of the parasympathe- 

 tic fibres, as will be shown below. 



STRUCTURAL CHANGES 



Claude Bernard (1864) observed that the submaxillary gland 

 diminishes in size after section of the chorda tympani, and this 

 has been confirmed by numerous later investigators (Bidder, 1867; 

 Heidenhain, 1868; Langley, 1885a; Bradford, 1888; Maximow, 

 1901; Chang and Gaddum, 1933; Macintosh, 1937; Emmehn, 

 Jacobsohn and Muren, 195 1 ; Stromblad, 1955*). The gland seems 



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