Elementary properties of axonal calcium currents in type B photoreceptors in Hermissenda crassicornis

Catherine T. Tamse, Ebenezer N. Yamoah

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Axons of the type B photoreceptors form synapses with hair cells and interneurons that are involved in classical conditioning in Hermissenda. We examined the differences in the Ca2+ channels expressed in the soma and axons of the B photoreceptors by direct functional recordings of single-channel currents. Although the soma of the B cells express two Ca2+ current subtypes, a transient BayK 8644-insensitive (-17 pS) current and a sustained BayK 8644-sensitive (∼10 pS) current, the axons expressed only the latter. The axonal Ca2+ current activated at potentials positive to -20 mV. Moreover, the Ca2+ channels are distributed heterogeneously along the length of the axon, with the higher channel density (∼10-15 channel μm-2) occurring at the distal one-third of the isolated axons, with respect to the soma. The regions of Ca2+ channel clusters may represent the presynaptic site of the photoreceptor-interneuron synapses. Furthermore, the high-density clusters of Ca2+ channels may augment postsynaptic responses. The results of the present study represent the first direct recordings of Ca2+ currents at presumed synaptic sites. Expression of different Ca2+ channel subtypes at distinct compartments of the type B photoreceptors may generate diverse Ca2+ domains that may be required for neuronal plasticity in Hermissenda.

Original languageEnglish (US)
Pages (from-to)10533-10538
Number of pages6
JournalJournal of Neuroscience
Volume22
Issue number24
StatePublished - Dec 15 2002

Keywords

  • Calcium currents
  • Hermissenda
  • Learning
  • Memory
  • Neuronal plasticity
  • Photoreceptors
  • Presynaptic calcium channels

ASJC Scopus subject areas

  • Neuroscience(all)

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