Drugs with Ganglionic Actions 77 



Central inhibition of salivary secretion caused by general anaes- 

 thetics has already been mentioned. Some of these drugs, for 

 instance, certain barbiturates, may in addition exert an inhibitory 

 action on ganglia and more peripheral structures, as will be dis- 

 cussed below. Salivation as a component of the nausea syndrome 

 will be counteracted by antiemetic drugs, such as the antihista- 

 mines; some of these may further decrease the flow of saliva by 

 virtue of a parasympatholytic action. 



DRUGS WITH GANGLIONIC ACTIONS 



Drugs exciting ganglion cells may cause a secretion both via the 

 parasympathetic and the sympathetic postganglionic neurones ; the 

 biggest effects are obviously elicited via the former system. Simi- 

 larly, drugs interfering with synaptic transmission may do so in 

 both systems, but since secretion elicited from the central nervous 

 system is mainly mediated by the parasympathetic nerves, the most 

 important effect will be exerted on the synapse of that pathway. For 

 example, xerostomia during treatment of hypertension with a gan- 

 glionic blocking compound will be due to an action of the drug 

 exerted on the parasympathetic ganglion. 



The ganglionic synapse in both the sympathetic and the para- 

 sympathetic system is cholinergic and both types of ganglia can be 

 excited by acetylcholine. The muscarinic effect of this agent on the 

 salivary glands is, however, so pronounced that when ordinary 

 doses of acetylcholine are used to produce secretion, the concen- 

 tration required for a nicotinic effect is scarcely attained. This is 

 evidenced by the fact that the secretory effect of acetylcholine in 

 doses commonly used is not lowered by a ganglionic blocking agent. 

 The same seems to be true for tetramethylammonium. Burn and 

 Dale (191 5) found this compound to cause a marked secretion of 

 saliva in cats after intravenous injection. It was shown on various 

 structures to possess both muscarinic properties and to excite 

 ganglion cells ; but doses of nicotine sufficient to paralyse all gan- 

 glion cells hardly affected its action on the submaxillary gland. 



Nicotine injected intravenously was found by Heidenhain (1872) 

 to cause a transient salivary secretion in dogs ; afterwards neither 

 stimulation of the chorda nor of the cervical sympathetic nerve 

 caused any secretory response. Langley (1890) confirmed this find- 

 ing and found that local application of nicotine to the chorda close 

 to the submaxillary gland likewise produced a temporary secretion 



