AUTONOMIC NEUROEFFECTOR TRANSMISSION 23 1 



FIG. 12. Tests of a perfusate of physostigminized Locke's solution passing through the vessels of 

 the stomach of a dog during vagal stimulation. The samples collected before stimulation were slightly, 

 if at all, active. A: effects on the arterial pressure of a physostigminized cat under chloralose. B: 

 isolated frog heart (Straub). C: physostigminized rectus abdominis of the frog. D : physostigminized 

 leech muscle. In each series, B shows the effect of the perfusate collected during vagal stimulation ; 

 A and C correspond to two strengths of acetylcholine (C is double A'). [From Dale & Feldberg 

 (300 



be mentioned the heart and the sahvary glands 

 (61, 134) in physostigminized animals. Particularly 

 illuminating were the experiments by Feldberg & 

 Krayer (44) who showed that blood from the coronary 

 veins of physostigminized animals produced a con- 

 traction of the leech muscle shortly after vagal stimu- 

 lation. This effect was abolished by atropine and the 

 active substance was destroyed by blood. Even re- 

 flexly released transmitter was demonstrated in this 

 way. 



Although the cholinergic transmitter has not been 

 identified with the same certainty as the adrenergic 

 one, the sum of evidence obtained by indirect methods 

 leaves no serious doubt that it is either acetylcholine 

 or some other choline ester with very similar action 



(15)- 



In the autonomic neurotransmission to the salivary 

 glands both adrenergic and cholinergic fibers seem to 

 take part. By studying the distribution of cholin- 

 esterase Koelle (75) found in the cat, rabbit and 

 rhesus monkey that the concentration of the true 

 cholinesterase was higher in cholinergic neurons 

 than in adrenergic and sensory neurons. Cholin- 



esterase was also found to form a fine network around 

 the outside of the acini while it was not found in the 

 acinar cells (118). The network is united with the 

 nerve trunk and is considered to be cholinergic in the 

 submaxillary gland and adrenergic in the sublingual 

 gland. 



Occurrence, Biosynthesis and Storage 



It may be assumed that, if the postganglionic nerve 

 endings release acetylcholine during nerve stimula- 

 tion, this has been synthesized and stored in the axon. 

 For this reason acetylcholine would be expected to 

 occur as a natural constituent of cholinergic nerves. 

 In this connection only the postganglionic fibers are 

 being considered. Analysis of the acetylcholine con- 

 tent of such fibers has shown large amounts in the 

 short ciliary nerves, 3 to 8 /ng per gm, which is only 

 a little less than the amounts found in motor nerve 

 fibers or in preganglionic fibers (92, 125). The figures 

 are much higher than the acetylcholine content in 

 postganglionic sympathetic fibers, such as the splenic 

 nerve where the acetvlcholine-like action onlv corre- 



