Sympathomimetic Agents 83 



SYMPATHOMIMETIC AGENTS 



Salivary secretion is not one of the more conspicuous effects of 

 sympathomimetic agents. Chang (1937) compared the sensitivity of 

 different effectors to adrenaline in cats and gave the following order 

 of susceptibility: blood-sugar, blood pressure, denervated heart, 

 nictitating membrane, stomach, iris, hair and salivary gland. 



In general the sympathomimetic drugs are much less effective 

 than the parasympathomimetic in producing secretion of saliva. 

 This is probably parallel to the fact that the sympathetic inner- 

 vation is much less complete than the parasympathetic one. Glands 

 which respond well to sympathetic stimulation, such as the sub- 

 maxillary gland of the cat, do so to injected sympathomimetic 

 agents also ; exceptional submaxillary glands of the cat which do 

 not react to sympathetic stimulation are not stimulated by adren- 

 aline either. The secretory responses of the cat parotid gland are 

 small both when the sympathetic is stimulated and adrenaline is 

 injected (Stromblad, 1955). In rabbits, conversely, the parotid but 

 not the submaxillary gland responds well to adrenaline and sym- 

 pathetic stimulation (Nordenfelt and Ohlin, 1957). When the sub- 

 maxillary gland of a cat is relatively sensitive to adrenaline, so that 

 doses causing too disturbing vascular effects can be avoided, it can 

 be seen that adrenaline and sympathetic stimulation cause the same 

 maximal rate of secretion. 



Adrenaline can be shown to cause a secretion from the submaxil- 

 lary gland in man ; the drug has to be given through the salivary 

 duct in order not to produce any general effects (Emmelin and 

 Stromblad, 1954). 



On the gland cells adrenaline imitates the effect of sympathetic 

 stimulation, as seen in the microelectrode responses (Lundberg, 

 1955). In this connection it may be mentioned that one striking 

 difference between sympathetic and adrenaline saliva seems to 

 exist; after injection of adrenaline, glucose appears in the saliva. 

 This is generally not the case when the sympathetic nerve is 

 stimulated (Hebb and Stavraky, 1936). 



A series of sympathomimetic amines can be arranged, in order 

 of decreasing secretory activity on the submaxillary gland, as fol- 

 lows: adrenaline, noradrenaline, synephrin, ephedrine, paredrinol, 

 isoprenaline, amphetamine (Emmelin and Muren, 1951). The last 

 five drugs not only cause a secretion but also in some way increase 



