COMMENTS ON THE EXCITINE-INHIBITINE HYPOTHESIS 



383 



(3) The next question is: do soma and dendrite have a special receptor 

 tissue which corresponds to that of the motor end-plate; in other words, is 

 there acetylchoHne and end-plate type tissue in the grey matter? This does 

 indeed seem to be the case. When acetylcholine is appHed to the grey matter 

 from the outside only high concentrations cause convulsions. If acetylchoUne 

 is applied in a concentration of 0-5-2-0 m a seizure occurs with a latency of 

 5-30 sec. However, when it is accompanied by Bi, acetylcholine in a con- 

 centration in which it alone does not produce seizures, promotes the genera- 

 tion of excitine and results in a seizure with a latency of 10-20 min. Acetyl- 

 choUne has, however, a dual action, for it is antagonistic to the effect of 

 vitamin Be; it enhances the action of isonicotinic acid hydrazide (INH) in 

 preventing production of inhibitine at soma and dendrites of central nerve 

 cells (see Table 2). 



Table 2. Motor effects of various substances on the grey 

 matters of dogs 



(4) The last question must be then: are excitine (NC) and the assumed 

 excitatory transmitter the same substances, and is inhibitine (NC) the same 

 as the inhibitory transmitter in the central motor system? The answer must 

 be yes. We conclude that the endings of the excitatory fibres attached to the 

 soma of the second cells secrete the excitine (NC) and that this affects the 

 soma in such a way as to produce excitation which travels over the pathway 

 which has its special excitine (P) and inhibitine (P). Likewise, the endings 

 of the inhibitory fibres liberate inhibitine (NC). This substance affects the 

 second cell to neutralize the excitine which the second cell has, produces, or 

 has received from another fibre. 



REFERENCES 

 DuBuissoN, M. (1954) Muscular Contraction. Charles C. Thomas, Springfield, Illinois. 

 26 



