Physiological recordings of high and low output NMJs on the crayfish leg extensor muscle

Wen Hui Wu, Robin L. Cooper

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We explain in detail how to expose and conduct electrophysiological recordings of synaptic responses for high (phasic) and low (tonic) output motor neurons innervating the extensor muscle in the walking leg of a crayfish. Distinct differences are present in the physiology and morphology of the phasic and tonic nerve terminals. The tonic axon contains many more mitochondria, enabling it to take a vital stain more intensely than the phasic axon. The tonic terminals have varicosities, and the phasic terminal is filiform. The tonic terminals are low in synaptic efficacy but show dramatic facilitated responses. In contrast, the phasic terminals are high in quantal efficacy but show synaptic depression with high frequency stimulation. The quantal output is measured with a focal macropatch electrode placed directly over the visualized nerve terminals. Both phasic and tonic terminals innervate the same muscle fibers, which suggests that inherent differences in the neurons, rather than differential retrograde feedback from the muscle, account for the morphological and physiological differentiation.

Original languageEnglish
Article numbere2319
JournalJournal of Visualized Experiments
Issue number45
StatePublished - Nov 2010


  • Crayfish
  • Invertebrate
  • Issue 45
  • Motor neuron
  • Muscle
  • Neuromuscular junction
  • Neuroscience
  • Synapse

ASJC Scopus subject areas

  • Neuroscience (all)
  • Chemical Engineering (all)
  • Biochemistry, Genetics and Molecular Biology (all)
  • Immunology and Microbiology (all)


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