T-type calcium channels mediate the transition between tonic and phasic firing in thalamic neurons

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Thalamic neurons undergo a shift from tonic to phasic (burst) firing upon hyperpolarization. This state transition results from deinactivation of a regenerative depolarizing event referred to as the low-threshold spike. Isolated adult guinea pig thalamic (dorsal lateral geniculate) neurons exhibited low-threshold spikes that could be blocked by low concentrations of nickel but were unaffected by the dihydropyridine nimodipine. Whole-cell voltage-clamp recordings from these cells demonstrated a low-threshold, rapidly inactivating (T) Ca2+ current that manifested similar voltage dependency and time course as the low-threshold spike. Like low-threshold spikes, the T-type Ca2+ current was eliminated by nickel but was unaffected by nimodipine. In thalamic neurons, T-type Ca2+ channels underlie the low-threshold spike and, therefore, play a critical role in regulating the firing pattern of these cells.

Original languageEnglish (US)
Pages (from-to)7228-7232
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number18
StatePublished - 1989
Externally publishedYes


ASJC Scopus subject areas

  • General
  • Genetics

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