Physiological Bases for Differing Synaptic Efficacy in Frog Neuromuscular Junctions

  • Peter A. Pawson
  • Alan D. Grinnell
Part of the Topics in the Neurosciences book series (TNSC, volume 1)


Neuromuscular junctions (NMJs) in the frog sartorius muscle differ over a 20-fold range in transmitter release per unit length of nerve terminal (Grinnell & Herrera, 1980). Part of the explanation for these differences in synaptic strength lies in the inherent release properties of different motor units (Grinnell & Trussell, 1983; Trussell & Grinnell, 1984). However, there are still considerable differences between junctions within the same motor unit. Moreover, this observation does not explain the physiological mechanisms responsible. Of further interest, a substantial body of research has shown that the adult neuromuscular junction can exhibit considerable structural and physiological plasticity (Grinnell & Herrera, 1981; Herrera & Grinnell, 1980,1981; Kelly & Robbins, 1983; Rotshenker, 1982; Smith, 1982; Wernig, Pecot-Dechavassine & Stover, 1980). This synaptic plasticity and the apparently dynamic motoneuron regulation that it implies (Nudell & Grinnell, 1982, 1983), suggests a comparison with the previously desscribed plasticity in the central nervous system (CMS) and spinal cord (Cotman, Nieto-Sampadro & Harris, 1981; Mendell, 1984). Since the frog neuromuscular junction has served as an important model for the transmitter release process (Katz, 1969), and because the CNS presents serious obstacles to a cellular analysis of the physiological and structural mechanisms responsible for synaptic plasticity, we have pursued an analysis of this problem at the frog NMJ.


Motor Unit Active Zone Transmitter Release Synaptic Strength Frog Neuromuscular Junction 
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© Martinus Nijhoff Publishing, Boston 1986

Authors and Affiliations

  • Peter A. Pawson
  • Alan D. Grinnell

There are no affiliations available

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