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Updated: Sep 28, 2026

Physiological Recordings of High and Low Output NMJs on the Crayfish Leg Extensor Muscle
Published on: November 17, 2010
Synaptic differentiation between two phasic motoneurons to a crayfish fast muscle
C K Govind1, P A Quigley, J Pearce
1Life Sciences Division, University of Toronto at Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada. govind@scar.utoronto.ca
Abstract:
Synaptic differentiation among crustacean phasic motoneurons was investigated by characterizing the synaptic output and nerve terminal morphology of the two axons to the adductor exopodite muscle in the crayfish uropod. The muscle is of the fast type with short sarcomeres (2-3 micro m) and a low thin to thick filament number (6:1). On single muscle fibers, excitatory postsynaptic potentials generated by the large-diameter axon are significantly larger than those by the small-diameter axon suggesting a presynaptic origin for these differences. Nerve terminals arising from these two axons have typical phasic features, filiform shape and a low (6-8%) mitochondrial density. Synaptic contacts are similar in size between the two axons as is the length and number of active zone dense bars at these synapses. The large-diameter axon, however, exhibits a twofold larger area of nerve terminal than the small-diameter axon resulting in a higher density of synapses per muscle fiber. Hence, differences in synaptic density may in part account for differences in synaptic output between these paired phasic axons.
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