Electrical synaptic transmission in developing zebrafish: properties and molecular composition of gap junctions at a central auditory synapse

J Neurophysiol. 2014 Nov 1;112(9):2102-13. doi: 10.1152/jn.00397.2014. Epub 2014 Jul 30.


In contrast to the knowledge of chemical synapses, little is known regarding the properties of gap junction-mediated electrical synapses in developing zebrafish, which provide a valuable model to study neural function at the systems level. Identifiable "mixed" (electrical and chemical) auditory synaptic contacts known as "club endings" on Mauthner cells (2 large reticulospinal neurons involved in tail-flip escape responses) allow exploration of electrical transmission in fish. Here, we show that paralleling the development of auditory responses, electrical synapses at these contacts become anatomically identifiable at day 3 postfertilization, reaching a number of ∼6 between days 4 and 9. Furthermore, each terminal contains ∼18 gap junctions, representing between 2,000 and 3,000 connexon channels formed by the teleost homologs of mammalian connexin 36. Electrophysiological recordings revealed that gap junctions at each of these contacts are functional and that synaptic transmission has properties that are comparable with those of adult fish. Thus a surprisingly small number of mixed synapses are responsible for the acquisition of auditory responses by the Mauthner cells, and these are likely sufficient to support escape behaviors at early developmental stages.

Keywords: Mauthner cell; auditory development; connexin 35; connexin 36; escape response.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Auditory Pathways / growth & development
  • Auditory Pathways / physiology
  • Connexins / genetics
  • Connexins / metabolism
  • Electrical Synapses / physiology*
  • Gap Junction delta-2 Protein
  • Gap Junctions / metabolism
  • Gap Junctions / physiology*
  • Larva / growth & development
  • Larva / physiology
  • Rhombencephalon / growth & development
  • Rhombencephalon / physiology*
  • Synaptic Transmission*
  • Zebrafish


  • Connexins