Comparison of ionic currents expressed in immature and mature muscle cells of an ascidian larva

Anna K. Davis, Adrienne A. Greaves, Julia E. Dallman, William J. Moody

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


We have compared the voltage-gated ion channels present in larval ascidian muscle at two developmental stages: muscle precursor cells just after the terminal cell division and mature contractile muscle, 7-11 hr later. All precursor cells express a high-threshold transient Ca current and a slowly activating delayed K current, and about half the cells express a low- threshold transient Ca current. An inwardly rectifying K current, which had been present from fertilization until just before the terminal celt division, is absent. Mature muscle retains two of the tailbud currents: the low- threshold transient Ca current and the slow delayed K current, although at larger densities, and also expresses a high-threshold Ca current that is similar in most respects to the precursor cell current but that lacks inactivation. In addition, mature muscle expresses two rapidly activating outward K currents, one voltage and one Ca dependent, that generate a composite outward K current that is eight times larger and activates eight times faster then the tailbud K current. Mature muscle also reexpresses the inward rectifier. We propose that the transient absence of the inward rectifier and the slow activation of the delayed K current early in development create a window of developmental time when spontaneous electrical activity is likely.

Original languageEnglish (US)
Pages (from-to)4875-4884
Number of pages10
JournalJournal of Neuroscience
Issue number7 I
StatePublished - Jul 1995
Externally publishedYes


  • ascidian larva
  • Ca channel
  • delayed rectifier
  • development
  • ion channel
  • K channel
  • muscle

ASJC Scopus subject areas

  • Neuroscience(all)


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