NEUROMUSCULAR SYNAPTIC ACTIVITY 

 IN LOBSTER* 



Harry Grundfest and John P. Reuben! 



Department of Neurology, College of Physicians and Surgeons, 

 Columbia University, New York 



The neuromuscular systems of the legs of the lobster, H. americanus, offer 

 numerous possibilities for electrophysiological and pharmacological studies 

 of the elements that are involved in transmissional processes. At least one 

 inhibitory, and one or several excitatory axons innervate multiterminally the 

 fibers of each muscle. The axons are readily separated in the nerve trunk and 

 the properties of the conductile membrane of each nerve fiber thus may be 

 examined separately. Miniature postsynaptic potentials (p.s.p.'s) occur in 

 both the excitatory and inhibitory synaptic membranes of the muscle fibers 

 and their study permits some degree of analysis of events in the presynaptic 

 terminals, though the latter have as yet proved inaccessible to direct study 

 with microelectrode recordings. As will be described below, there appear to 

 be two distinct action components in the presynaptic terminal region (Reuben 

 and Grundfest, 1960c). Evoked excitatory and inhibitory p.s.p.'s that are 

 produced by stimulating the axons may be studied separately and in combina- 

 tion under various pharmacological and physiological conditions. Their 

 properties may be distinguished from those of the conductile membrane 

 by the distinctive differences between electrically inexcitable transmissional 

 and electrically excitable conductile activities (Grundfest, 1957a, 1959). 

 Furthermore, while the electrically excitable membrane is normally gradedly 

 responsive (Werman and Grundfest, 1961) it may be converted to all-or-none 

 activity by various means (Reuben and Grundfest, 1960a; Reuben e/ a/., 1960a; 

 Werman and Grundfest, 1961). It also exhibits a number of anomalous 

 properties and their analysis (Grundfest, 1960, 1961a; Reuben et al., 1960b) 

 has helped to throw considerable light on the various ionic mechanisms of 

 electrically excitable membrane (Grundfest, 1961a). Thus, interplays of in- 

 hibitory and excitatory processes need to be studied in greater detail than as 

 the interaction of only two sets of events in the postsynaptic cell. 



* These researches were supported in part by funds from the following sources: Muscular 

 Dystrophy Associations of America, National Institutes of Health, National Science 

 Foundation and United Cerebral Palsy Research and Educational Association. 



t Dr. Reuben is a Fellow of the National Science Foundation. 



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