62 Innervation of the Glandular Elements 



ganglionic synapses. There is evidence to show that acetylcholine 

 is continuously released from the postganglionic, parasympathetic 

 endings in the salivary glands, and it may exert some kind of action 

 on the gland cells (Emmelin, i960). 



In perfusion experiments with eserinized solutions acetylcholine 

 has been detected in the effluent when no nerves have been stimu- 

 lated (Henderson and Roepke, 19336, Emmelin and Muren, 1950). 

 This can be seen in Fig. 3.2. In these experiments impulses from 

 the central nervous system were excluded by section of the 

 (preganglionic) chorda fibres. Acetylcholine was obtained even 

 when curarine was present in the perfusion fluid, as shown in the 

 figure, and this could therefore not be due to impulses from the cut 

 end, for instance, or set up in the postganglionic cell body by the 

 eserine. 



Anticholinesterases are known to cause secretion of saliva. This 

 is the case even when the drugs are given into the artery of the 

 gland (Dirnhuber and Evans, 1954) or through the salivary duct 

 towards the gland (Emmelin, Muren and Stromblad, 1954); with 

 suitable doses the effect will remain local in the gland. The effect 

 is abolished by atropine. It can be elicited when the chorda fibres 

 have been cut, and is thus not dependent on impulses from the 

 central nervous system. It can even be evoked when the post- 

 ganglionic fibres have been sectioned acutely (Emmelin and Strom- 

 blad, 1958a); this was shown by section of the auriculo-temporal 

 fibres of the parotid gland. Consequently, the secretory effect of 

 anticholinesterases is not dependent on impulses from the post- 

 ganglionic cell body either. When the postganglionic fibres have 

 been cut in advance and been allowed to degenerate, on the other 

 hand, the effect of anticholinesterases is very small, in spite of the 

 fact that the gland cells, because of the denervation, are highly 

 supersensitive to acetylcholine. Fig. 3.8 shows the effect of eserine 



Nor(R) 

 Post (L) 



£ 



Fig. 3.8. Secretion from the normally innervated, right parotid gland of a cat 

 (Nor) and from the left parotid (Post); the left auriculo-temporal fibres had been 

 cut 18 days previously. 



Time in minutes. The signal (Sig) marks the injection of acetylcholine, 2 /'g/kg, intravenously 

 at A ; and the injection into the right (R) and left (L) parotid duct of 50 /<g eserine (£) (after 

 Emmelin and Stromblad, 1958). 



