380 TAKASHI HAYASHI 



isolated single nerve fibres were prepared, carnitine (0-005 m) in combination 

 with taurine (0-005 m) caused excitation which was recognized by the resulting 

 muscle contractions. Carnosine in combination with taurine (both 0-005 m) 

 had no detectable effect. We tried these and related substances on the central 

 nervous system, especially on the motor cortex. 



EUiott and Florey (1956) identified Factor I extracted from vertebrate 

 brain as y-aminobutyric acid (GAB A) and in the same year Hayashi and 

 Nagai declared that the inhibitine of the central motor system is y-amino-/3- 

 hydroxybutyric acid (GABOB). We tested both substances for their excitatory 

 and inhibitory action on the motor cortex. We did find that GABA as well 

 as GABOB has a strong inhibiting action on electrically induced seizures if 

 they are introduced into the cerebrospinal fluid or if they are rapidly intro- 

 duced through the carotid artery. We also found that GABOB was a con- 

 stituent of mammahan brain (Hayashi, 1958). 



We found that GABA could produce seizures in higher concentrations and 

 that it inhibited seizures if apphed in lower concentrations. We furthermore 

 found that GABA produced seizures in all cases when it was accompanied 

 by vitamin B12 and Bi ; and we showed that it always produced inhibition if 

 accompanied by vitamin Be. We, therefore, beheved that GABA might be 

 the mother substance of excitatory as well as inhibitory transmitter (Hayashi, 

 1959). Although the structure of the former is not yet elucidated, the latter 

 is definitely GABOB. 



Previously we have used synthetic dl-GABOB, but recently we have used 

 L-GABOB and found that the inhibitory actions of the two compounds are 

 related as one to three; that is, l-GABOB is a stronger inhibitor than dl- 

 GABOB. 



The extraction of excitine from the brain of vertebrates has been tried by 

 many authors, but the results were dubious since it was not known that the 

 substance exists in free form in the normal condition of the brain. Several 

 years ago we succeeded in extracting it from cerebral spinal fluid of dogs 

 during electrically induced seizures. For convenience, we named the active 

 principle "excitine NC". Generalized seizures were produced by direct 

 electrical stimulation of the exposed surface of the motor cortex or by applica- 

 tion of electro-shock current apphed through the scalp of dogs. The induced 

 seizures lasted from 60 to 180 sec after the cessation of stimulation. When 

 1-3 ml of cerebral spinal fluid were taken during the seizure and introduced 

 into the cerebrospinal fluid of another dog, a generafized seizure occurred in 

 the receiver dog. 



If the fluid was taken 3-4 min after cessation of the seizures, no seizures 

 were produced if such fluid was transferred to another dog. In fact, the 

 excitatory substance seems to be quite labile since out of twelve cases we 

 could obtain the substance in only one or two cases. 



We have attempted to discover the reason for the rapid disappearance of 



