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Published on: February 10, 2012

Flickering of a nicotinic ion channel to a subconductance state

A Auerbach, F Sachs

    Biophysical Journal
    |April 1, 1983
    PubMed

    Insights

    Researchers studied nicotinic acetylcholine receptor channel flickers, finding most are not fully closed. These flickers represent distinct sub-conductance states, not a prerequisite for channel opening.

    Area of Science:

    • Neuroscience
    • Molecular Biology
    • Biophysics

    Background:

    • Nicotinic acetylcholine receptors (nAChRs) mediate fast synaptic transmission.
    • Channel activity is characterized by bursts of openings separated by brief closures (flickers).
    • Flickers are hypothesized to represent transitions to pre-opening closed states.

    Purpose of the Study:

    • To investigate the amplitude distribution of flickers in nAChRs.
    • To determine the nature of sub-conductance states during channel flickers.
    • To clarify the role of flickers in the channel gating cycle.

    Main Methods:

    • Utilized tissue-cultured chick pectoral muscle for electrophysiological recordings.
    • Analyzed the amplitude distribution of flicker events.
    • Measured current amplitudes of flickers with sufficient duration for accurate assessment.

    Main Results:

    • Approximately 25% of flickers were long enough for amplitude measurement.
    • Two-thirds of measurable flickers exhibited a sub-conductance state (10% of fully open current).
    • One-third of flickers showed complete closure, and a short flicker type (0.1 ms) had uncertain current distribution.

    Conclusions:

    • Flickers represent at least two distinct longer-lived states (0.1 ms and 1 ms), one sub-conducting and one non-conducting.
    • The sub-conducting flicker state is not essential before channel opening.
    • Local anesthetic QX-222-induced flickers are indistinguishable from zero current, suggesting a different mechanism.

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