THE INHIBITORY SUBSTANCE EXTRACTED FROM BRAIN 



373 



activity produced by strychnine. The monopolar leads were recorded in 

 succinylchohne paralysis, in the waking state. The amphtude of the negative 

 discharges produced by the local application of a 1-0% strychnine solution 

 was decreased by locally administered GABA or G ABOB of 1 mg/ml concen- 

 tration, which confirmed earher observations on the subject by Purpura et al. 

 (1958). A similar result was obtained when the brain extract was applied. 

 Intravenously administered GABA or GABOB did not influence the de- 

 polarizing dendritic potentials, while the intravenous administration of the 

 brain extract not only prevented the depolarizing activity, but also had a 

 transitory hyperpolarizing effect. Similar phenomena were also reported by 

 Iwama and Jasper (1957) further by Purpura and his co-workers (1958), 

 although it was only in the case of a blood-brain barrier destroyed by 

 methanol-chloroform and after the administration of large quantities of 

 GABA that those authors observed a similar effect. From the data in Fig. 4 



Fig. 4. Electrical activity produced by topical application of strychnine to the 

 cat's brain. Monopolar recording: different silver-ball electrode on the motor 

 cortex, indifferent electrode on the frontal bone. At arrow surface negative 

 activity was reversed by the intravenous administration of the brain extract. 



it may be seen that the brain extract can turn the initial depolarizing activity 

 into hyperpolarization. The development of the mechanism is unknown; 

 however, it is highly probable that in this experiment abohtion of the in- 

 hibitory effect of strychnine on axo-dendritic hyperpolarization plays an 

 important role. 



The action of the brain extract and that of GABA on subcortical structures 

 were studied on the conditional reflex activity of dogs with chronically 

 implanted microcannulas. The cannula was implanted, with the methods we 

 usually employ, after the establishment of a conditioned alimentary motor 

 reflex. In each of the four experimental animals the cannula was localized in 



