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Ca 2+ ‐dependent ion channels underlying spontaneous activity in insect circadian pacemaker neurons
Author(s) -
Wei Hongying,
Stengl Monika
Publication year - 2012
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2012.08227.x
Subject(s) - ion channel , circadian rhythm , neuroscience , tetrodotoxin , chemistry , sk channel , biophysics , cockroach , medicine , biology , receptor , biochemistry , ecology
Electrical activity in the gamma frequency range is instrumental for temporal encoding on the millisecond scale in attentive vertebrate brains. Surprisingly, also circadian pacemaker neurons in the cockroach Rhyparobia maderae ( Leucophaea maderae ) employ fast spontaneous rhythmic activity in the gamma band frequency range (20–70 Hz) together with slow rhythmic activity. The ionic conductances controlling this fast spontaneous activity are still unknown. Here, Ca 2+ imaging combined with pharmacology was employed to analyse ion channels underlying spontaneous activity in dispersed circadian pacemakers of the adult accessory medulla, which controls circadian locomotor activity rhythms. Fast spontaneous Ca 2+ transients in circadian pacemakers accompany tetrodotoxin (TTX)‐blockable spontaneous action potentials. In contrast to vertebrate pacemakers, the spontaneous depolarisations from rest appear to be rarely initiated via TTX‐sensitive sustained Na + channels. Instead, they are predominantly driven by mibefradil‐sensitive, low‐voltage‐activated Ca 2+ channels and DK‐AH269‐sensitive hyperpolarisation‐activated, cyclic nucleotide‐gated cation channels. Rhythmic depolarisations activate voltage‐gated Na + channels and nifedipine‐sensitive high‐voltage‐activated Ca 2+ channels. Together with Ca 2+ rises, the depolarisations open repolarising small‐conductance but not large‐conductance Ca 2+ ‐dependent K + channels. In contrast, we hypothesise that P/Q‐type Ca 2+ channels coupled to large‐conductance Ca 2+ ‐dependent K + channels are involved in input‐dependent activity.