Cellular and molecular characterization of Ca2+ currents in acutely isolated, adult rat neostriatal neurons

Jose Bargas, Angela Howe, James Eberwine, Y. Cao, D. James Surmeier*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

165 Scopus citations

Abstract

Ca2+ currents in acutely isolated, adult rat neostriatal neurons were studied with whole-cell voltage-clamp techniques. In the vast majority of neurons (~90%, n > 250), currents were exclusively of the high-voltage- activated (HVA) type. HVA currents activated near -40 mV and reached their maximum amplitude near 0 mV. Quasi-steady-state inactivation curves in many neurons were well fitted only with a sum of Boltzmann functions, suggesting that the HVA currents were heterogeneous. Although the block of whole-cell current by Cd2+ was well fitted with a single isotherm having an IC50 of near 1 μM, experiments with organic channel antagonists suggested that at least four types of HVA channels were expressed by most cells. On average, the L-channel antagonist nifedipine (5-10 μM) blocked 31 ± 10% of the whole-cell current (n = 20), the N-channel antagonist ω-conotoxin GVIA (ω- CgTx) (2-5 μM) blocked 27 ± 11% (n = 20), and the P-channel antagonist ω- agatoxin IVA (100-500 nM) blocked 21 ± 10% (n = 18). In many neurons, the block by ω-CgTx was partially or completely reversible. In cells tested with a combination of these antagonists, 34 ± 17% of the peak Ca2+ current remained unblocked (n = 13). Single-cell expression profiling of medium- sized neurons revealed the presence of rbA and rbB Ca2+ channel α1 subunit mRNAs but low or undetectable levels of rbC mRNA (n = 12). These findings suggest that although adult neostriatal projection neurons do not express significant levels of LVA Ca2+ current, they do express a pharmacologically and structurally heterogeneous population of HVA currents.

Original languageEnglish (US)
Pages (from-to)6667-6686
Number of pages20
JournalJournal of Neuroscience
Volume14
Issue number11 I
DOIs
StatePublished - 1994

Keywords

  • Ca current
  • dihydropyridine
  • mRNA profiling
  • neostriatum
  • voltage clamp
  • ω-agatoxin IVA
  • ω-conotoxin GVIA

ASJC Scopus subject areas

  • Neuroscience(all)

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