COMMENTS ON THE EXCITINE-INHIBITINE HYPOTHESIS 

 Table 1. Existence of certain substances in vertebrate muscle 



OR brain (%) 



379 



(2) L-Carnosine in isotonic sodium chloride solution (0-30%) stops the 

 muscle contractions occurring in an isolated toad's sartorius muscle bathed 

 in isotonic sodium chloride solution. This inhibitory action of L-carnosine is 

 not enhanced by addition of glutamic acid, aspartic acid or cysteine, but it is 

 definitely enhanced by the addition of taurine (0-075%) and acetylcholine 

 (0-000025 %). The concentrations necessary to enhance the inhibitory action 

 of L-carnosine are less than those in which these substances are normally 

 present in muscle. 



(3) If 0-0147% carnitine is combined with 0-25% carnosine in the presence 

 of 0-075 °o taurine, the mixture is completely ineffective if applied to an 

 excised muscle. 



We conclude that the true excitine is carnitine in combination with taurine 

 and that the true inhibitine is carnosine in combination with taurine. 



It is possible to separate the excitine from the inhibitine by the application 

 of electric current as indicated in Fig. 1 . The current from a 2 V dry cell 

 applied for 5 sec is sufficient to cause the appearance of excitine in the anodal 

 fluid (as tested on a freshly excised toad sartorius muscle) and the appearance 

 of inhibitine in the cathodal fluid (as shown by the abihty of this fluid to 

 inhibit the contractions of a muscle subjected to isotonic sodium chloride 

 solution). 



These facts permit the conclusion that electric current which stimulates a 

 live muscle can dissociate the excitine-inhibitine complex and explains why 

 a contraction should occur at the cathode of the stimulating electrodes. 



THE INHIBITINE (NC) AND EXCITINE (NC) OF 

 THE CENTRAL MOTOR SYSTEM 



Carnitine as well as carnosine was found to have no effect on excised nerves 

 of toads and frogs. However, when part of the nerve was desheathed or when 



