Intrinsic differences in sensitivity to 5-HT between high- and low-output terminals innervating the same target

Robin L. Cooper, Ahmet Dönmezer, Joseph Shearer

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The differential action of neuromodulators on synapses of various efficacy provides additional fine tuning of synaptic regulation beyond frequency induced plasticity. We used the well-characterized high- and low-output motor nerve terminals, of the tonic and phasic neuromuscular junctions (NMJs) in the walking leg extensor muscle of the crayfish, to investigate differential actions of serotonin (5-HT) since both terminals innervate the same target. The excitatory postsynaptic potentials of the tonic NMJ are enhanced to a greater extent than for the phasic NMJs during exposure to 5-HT (100 nM). Macropatch current recordings at identified sites along the motor nerve terminals and quantal analysis indicate that mean quantal content is substantially increased by 5-HT. The overall probability of vesicular release increases to a greater extent at tonic terminals than at phasic terminals when exposed to 100 nM 5-HT. Measures in the area (i.e. charge) of spontaneous quantal currents indicate no difference in postsynaptic receptivity to the glutamatergic synaptic transmission upon exposure to 5-HT. The results provide new details concerning differential modulation of low- and high-output synapses present on the same target tissue.

Original languageEnglish
Pages (from-to)163-172
Number of pages10
JournalNeuroscience Research
Issue number2
StatePublished - Feb 1 2003

Bibliographical note

Funding Information:
Appreciation is given to Hye Won Cooper for illustrative work. Support was provided by a Ribble Fellowship and an Interdepartamental Neuroscience Program training fellowship, University of Kentucky, Department of Biology (J.S.) and NSF grants IBN-9808631, ILI DUE-9850907 and IBN-0131459 (R.L.C.).


  • Crayfish
  • Neuromuscular junction
  • Neurotransmission
  • Serotonin
  • Synapse

ASJC Scopus subject areas

  • General Neuroscience


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