Control of phasic firing by a background leak current in avian forebrain auditory neurons

André A. Dagostin, Peter V. Lovell, Markus M. Hilscher, Claudio V. Mello, Ricardo M. Leão

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Central neurons express a variety of neuronal types and ion channels that promote firing heterogeneity among their distinct neuronal populations. Action potential (AP) phasic firing, produced by low-threshold voltage-activated potassium currents (VAKCs), is commonly observed in mammalian brainstem neurons involved in the processing of temporal properties of the acoustic information. The avian caudomedial nidopallium (NCM) is an auditory area analogous to portions of the mammalian auditory cortex that is involved in the perceptual discrimination and memorization of birdsong and shows complex responses to auditory stimuli We performed in vitro whole-cell patch-clamp recordings in brain slices from adult zebra finches (Taeniopygia guttata) and observed that half of NCM neurons fire APs phasically in response to membrane depolarizations, while the rest fire transiently or tonically. Phasic neurons fired APs faster and with more temporal precision than tonic and transient neurons. These neurons had similar membrane resting potentials, but phasic neurons had lower membrane input resistance and time constant. Surprisingly phasic neurons did not express low-threshold VAKCs, which curtailed firing in phasic mammalian brainstem neurons, having similar VAKCs to other NCM neurons. The phasic firing was determined not by VAKCs, but by the potassium background leak conductances, which was more prominently expressed in phasic neurons, a result corroborated by pharmacological, dynamic-clamp, and modeling experiments. These results reveal a new role for leak currents in generating firing diversity in central neurons.

Original languageEnglish (US)
Article number471
Pages (from-to)1-17
Number of pages17
JournalFrontiers in Cellular Neuroscience
Volume9
Issue numberDEC
DOIs
StatePublished - Dec 10 2015

Keywords

  • Action potentials
  • Birdsong
  • Leak current
  • Potassium currents
  • Zebra finch

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience

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