NEUROHORMONES 165 



Such methods have been appHed recently in identifying choline esters and 

 catechol and indole amines in certain invertebrates. Three examples will 

 be cited. 



Ostlund (1954) has cleared up the uncertainty over the question of the 

 occurrence of adrenaline in insects. By means of chromatographic separa- 

 tion, followed by elution and bioassay, he has found adrenaline, nor-ad- 

 renaline, and dopamine in a variety of insects. Adrenaline is present in 

 least amount, while dopamine is most abundant of the three. In two lots of 

 whole mealworms (Tenebrio larvae) adrenaline was present in amounts of 

 0.021 and 0.061 fig/gm., nor-adrenaline in amounts of 1.3 and 2.2 /^g/gm., 

 while dopamine values were between 10-15 /i,g/gm. in both lots. Ostlund 

 suggests that the presence of relatively large amounts of dopamine may 

 indicate that it is the precursor of nor-adrenaline. A similar origin of nor- 

 adrenaline has been proposed in the vertebrates. 



A second example also comes from recent studies on insects. Various 

 earlier workers (e.g., Corteggiani and Serfaty, 1939; Mikalonis and 

 Brown, 1941) reported large amounts of acetylcholine in certain insect 

 nervous systems. Recently some question had arisen regarding the true 

 identity of the acetylcholine-like substance in insects. Now, however, 

 Augustinsson and Grahn (1954), using chromatography, have found 

 acetylcholine in the head of the honeybee. They also have evidence for the 

 presence of one or two other unidentified esters of choline. 



In another invertebrate phylum, paper chromatography has been suc- 

 cessfully applied in the identification of a biologically active substance 

 present in nerve tissue. Earlier observations had suggested that 5-hy- 

 droxytryptamine might be a mediator of the cardiac accelerator neurons to 

 the heart of Venus mercenaria (Welsh, 1953). Chromatography revealed 

 the presence of this indole amine in nerve ganglia of Venus. We now have 

 evidence for its occurrence in nerve tissue of the gastropod, Busycon, the 

 lamellibranchs, Venus, Mactra, and Ensis, and the cephalopods, Loligo 

 and Octopus (two species). 



At the present time it appears that the neurohumors of the invertebrates 

 are, perhaps, only slightly more varied than those of the vertebrates. In 

 addition to acetylcholine, there may be certain other choline esters or, 

 possibly, simpler quaternary ammonium compounds acting as acetylcho- 

 line-like agents. Much of the evidence for the presence and normal action 

 of catechol amines in the invertebrates requires confirmation. The occur- 

 rence of the indole amine, 5-hydroxytryptamine, which often has an ad- 

 renaline-like activity and which originates in chromaffin cells, as does 

 adrenaline, makes it imperative that the identity of the biologically active 

 amines in the invertebrates be given closer scrutiny. 



We know next to nothing regarding the chemical nature of the neuro- 



