• Media type: E-Article
  • Title: Excitatory Synaptogenesis between IdentifiedLymnaeaNeurons Requires Extrinsic Trophic Factors and Is Mediated by Receptor Tyrosine Kinases
  • Contributor: Hamakawa, Toshiro; Woodin, Melanie A.; Bjorgum, Micki C.; Painter, Sherry D.; Takasaki, Mayumi; Lukowiak, Ken; Nagle, Gregg T.; Syed, Naweed I.
  • imprint: Society for Neuroscience, 1999
  • Published in: The Journal of Neuroscience
  • Language: English
  • DOI: 10.1523/jneurosci.19-21-09306.1999
  • ISSN: 0270-6474; 1529-2401
  • Keywords: General Neuroscience
  • Origination:
  • Footnote:
  • Description: <jats:p>Neurotrophic factors have well established roles in neuronal development and adult synaptic plasticity, but their precise role in synapse formation has yet to be determined. This paper provides the first direct evidence that neurotrophic factors in brain conditioned medium (CM) differentially regulate excitatory and inhibitory synapse formation. Somata of identified presynaptic and postsynaptic neurons were isolated from the CNS of<jats:italic>Lymnaea</jats:italic>and were cultured in a soma–soma configuration in the presence (CM) or absence [defined medium (DM)] of trophic factors. In DM, excitatory synapses did not form. When they were paired in CM or in DM containing<jats:italic>Lymnaea</jats:italic>epidermal growth factor (EGF); however, all presynaptic neurons reestablished their specific excitatory synapses, which had electrical properties similar to those seen<jats:italic>in vivo</jats:italic>. CM-induced formation of excitatory synapses required transcription and<jats:italic>de novo</jats:italic>protein synthesis, as indicated by the observations that synapse formation was blocked by the protein synthesis inhibitor anisomycin and the protein transcription blocker actinomycin D; the CM factor was inactivated by boiling. They were also blocked by receptor tyrosine kinase inhibitors (lavendustin A, genistein, K252a, and KT5926) but not by inactive analogs (genistin and lavendustin B), suggesting that the effect was mediated by receptor tyrosine kinases. These results, together with our previously published data, demonstrate that trophic factors are required for excitatory, but not inhibitory, synapse formation and extends the role of EGF from cell proliferation, neurite outgrowth, and survival to excitatory synapse formation.</jats:p>
  • Access State: Open Access