90 D. NACHMANSOHN VOL. 4 (1950) 



in support of Erlanger's views that the basic mechanism of transmission and con- 

 duction is the same, the propagating agent being in both cases the flow of current. 

 According to Eccles^^, impulses travelling down the pre-synaptic fibre, generate a 

 current which produces in the synaptic membrane of the post-synaptic cell an anodal 

 focus with cathodal surround; this is followed in a second phase by a more intense 

 cathodal focus with anodal surround. The cathodal focus sets up a local response from 

 which a catelectrotonus spreads over the post-synaptic cell membrane. The catelectro- 

 tonus, the end plate potential, sets up a propagated impulse in the post-synaptic cell 

 as soon as a certain threshold is reached. The sequence of events is similar to that 

 observed on artificial synapses and. on a single unit preparation of the synapse, the 

 stellate ganglion of Squid (Bullock^'). Since the electrical signs and the biochemical 

 data favor the assumption that the mechanism of transsynaptic transmission is basically 

 the same as that of conduction, it follows that the role of acetylcholine in these mecha- 

 nisms is most likely the same. In both cases the propagating agent is the flow of current, 

 but the release and the removal of acetylcholine must be essential events in the alteration 

 of the pre- and post-synaptic membrane during the flow of current across the synaptic 

 region and the generation of the end plate potential. It would be difficult to picture 

 these currents as being different in nature from those in the axons. A few biochemical 

 data may be mentioned in this connection which support the assumption of a high rate 

 of acetylcholine metabolism in the post-synaptic membrane of the motor end plate. 

 CouTEAUX AND Nachmansohn^^' ®^^ found that, following the section of the sciatic 

 nerve of guinea pigs, the high concentration of acetylcholine-esterase of the motor end 

 plates of the gastroncemius decreases only slightly. Within three to four weeks after 

 the operation one-fourth or possibly less of the enzyme concentration had disappeared. 

 Then the activity remains constant for many months. This result suggests that three 

 quarters of the enzyme or more is localized in the post-synaptic membrane, the "sole 

 plate" of KiJHNE, a pure muscular element which persists after the disappearance of all 

 nerve elements. 



The electric organs have physiologically evolved from striated muscle. The electric 

 plates are homologous with the motor end plate. The discharge of these organs is homo- 

 logous with the end plate potential. Recent studies of Couteaux^^^ have revealed that 

 the post-synaptic membrane of the motor end plate is morphologically a very peculiar 

 structure. By using Janus green or methyl violet, he demonstrated a striking similarity 

 with the electrolemma of the electric plate surrounding the nerve endings. The direct 

 proportionality between the voltage developed during the discharge and the concen- 

 tration of acetylcholine-esterase observed in the electric tissue suggests a high rate of 

 acetylcholine metabolism associated with the end plate potential. 



These findings alone without all the other evidence accumulated would not neces- 

 sarily imply that the acetylcholine is released in the post-synaptic membrane itself. 

 The following observations are, however, of interest in this connection. The discovery 

 of the extraordinarily high concentration of acetylcholine-esterase in electric tissue made 

 possible the assumption that acetylcholine might be the agent that produces the depolari- 

 zation presumably occurring during the action potential. The possibility of a depolarizing 

 action of acetylcholine has been considered by Dubuisson and Monnier'^" and Cowan'^. 

 In 1938, when the prerequisite for such a theory, namely the high speed of destruction 

 of the active agent appeared established. Auger and Fessard tested the effect of eserine 

 on the discharge of the electric tissue of Torpedo marmorata'^. As may be seen in Fig. 3 

 References p. 93/95. 



