INHIBITORY TRANSMITTERS — A REVIEW 



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Mention should also be made of extracts of brain which have been made 

 by two other groups of workers (Pataky and Pfeifer, 1955; Pfeifer and 

 Pataky, 1955; Lissak and Endroczi, 1956; Lissak et al., 1957) and which have 

 some similarities to and some differences from Factor I. Some of the 

 properties described for these various extracts are summarized in Table 1. 



It seems quite possible that both Pfeifer and Pataky, and Lissak and 

 Endroczi are in fact dealing with extracts which contain Factor I. Two 

 principal differences between Factor I and Lissak and Endroczi's material 

 are: (a) that the latter is described as soluble in organic solvents, whereas 

 Factor I is not; and (b) that relatively very large amounts of brain had to be 

 used by Lissak and Endroczi for an active extract to be obtained. A small 



Table 1. Some properties of brain extracts exhibiting inhibitory actions 



Acetylcholine contractions of ' Ileum: inhibited 



isolated intestine j at pH < 7 



Transmission through No action 

 superior cervical ganglion 



Neuromuscular transmission No action 



Strychnine convulsions Prevented 



Monosynaptic spinal reflexes Inhibited 



Ileum: inhibited at 

 pH<7 



Inhibited 



Inhibited 

 Prevented 

 Inhibited 



Ascending colon; 

 inhibited 



amount of water contained in the organic solvents used by Lissak and 

 Endroczi might have been sufficient to extract some Factor I from the brain. 

 However, the fact that their extract caused block of transmission in the 

 superior cervical ganglion and at neuromuscular junctions while Factor I 

 does not, may reflect real differences in the composition of the active material. 

 Two other workers have described evidence for inhibitory agents produced 

 by the brain, i.e. Kornmiiller (1958), and Wasserman (1954). The relation- 



