FURTHER OBSERVATIONS CONCERNING THE 

 INHIBITORY SUBSTANCE EXTRACTED FROM 



BRAIN 



K. LissAK, E. Endroczi and E. Vincze 



Physiological Institute, University of Pecs, Hungary 



One of the characteristics of neurophysiological research work in tlie past 

 decade has been the great interest in inhibitory processes, functional as well 

 as morphological, in which the recognition of direct inhibiting synaptic 

 mechanisms, i.e. that of an inhibitory transmitter substance of such character, 

 constitutes the central question. Without going into the exceedingly increased 

 number of pubhcations on the subject, we wish to refer to some of the 

 characteristic data in the literature pertinent to the chemical mediator as- 

 sumed to play a role in the inhibitory process. 



It was more than a decade ago that we first examined in our laboratory 

 the question whether or not the brain tissue contained a substance, or sub- 

 stances, which were able to inhibit the effect of stimulating chemical mediators 

 on peripheral receptors — thus on isolated cat's ileum and uterus, on frog's 

 heart — and further, if appHed locally, it could inhibit the excitability of the 

 spinal cord and decrease the electrical excitabiUty of the motor cortex (Lissak 

 and Endroczi, 1949, 1955, 1956a, b, 1957). 



Almost simultaneously with these investigations, but independently of 

 them, observations were pubUshed by Florey (1953, 1956), Florey and 

 McLennan (1956), Bazemore et al. (1956) according to whom the brain 

 tissue contained an I (inhibitor) factor which could produce inhibition on 

 receptors of Crustacea as well as on those of the central nervous system of 

 mammals. Starting with considerations of a different kind. Hayashi and 

 Nagai (1956) suggested that the inhibitory factor might be identical with 

 y-amino-/3-hydroxybutyric acid, considerable quantities of which were 

 present in the brain tissue. Bazemore et al. (1956) ascribed the inhibitory 

 effect of the brain extract studied by them to the action of y-aminobutyric 

 acid alone. However, McLennan (1957, 1958) and, on the basis of our own 

 observations made in the past years, we also have stated that GABA alone 

 cannot be responsible for the biological effects. Similarly, y-amino-/3- 

 hydroxybutyric acid may not be regarded as a factor which would be able to 

 simulate the effect of the natural inhibitory extract from the brain (Lissak et 

 al., 1959). 



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