102 



HARRY GRUNDFEST AND JOHN P. REUBEN 



ization 



Fig. 11. Effect of change of membrane potential on the amplitude of the large 

 e.p.s.p. produced in muscle fibers soaked in Cs~-Ringer"s solution. Six muscle 

 fibers from different preparations, each indicated by a different symbol. The origin 

 of the abscissa is the resting potential which was about - 75 m V in all experiments. 

 The reversal potential, as estimated by extrapolation, was at about — 20mV. 

 The slopes of the lines average about • 5 and indicate that the conductance change 

 during the e.p.s.p. decreased the membrane resistance to about half. 



physiological properties of the transmissional systems and of their interactions 

 have been given elsewhere (Grundfest, 1957a, b, c. 1958, 1959, 1961b). The 

 properties of the electrically excitable membrane and their various com- 

 plexities are also described elsewhere (Grundfest, 1960; 1961a; Reuben and 

 Grundfest, 1960a; Werman and Grundfest, 1961). 



It is of considerable interest to note that the pharmacological properties 

 differ markedly from those of another decapod crustacean, the crab (Florey 

 and Hoyle, 1961). Indeed, there also seem to be some differences between 

 the neuromuscular synapses of crayfish (Boistel and Fatt, 1958) and those 

 of lobster, but the data on the former are still insufficiently detailed for a 

 close comparison. The different actions of GABA and picrotoxin on the 

 presynaptic terminals and on the synaptic membrane in lobster indicate that 

 general conclusions cannot be drawn about the effects of various drugs. 

 Thus, while the axodendritic excitatory and inhibitory synapses of the 

 mammahan cortex are affected in a specific manner by the oi-amino acids 

 and related compounds (Purpura et ah, 1959), they affect various neuraxial 

 sites of bullfrog differently (Sigg and Grundfest, 1959). The electrophoretic 

 application of various amino acids on spinal neurons (Curtis, 1961) also 



