Journal
CELL REPORTS
Volume 34, Issue 5, Pages -Publisher
CELL PRESS
DOI: 10.1016/j.celrep.2021.108714
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Funding
- NHLBI [R01 HL148004, R01 HL108609, F31 HL154660]
- CCHS Family Foundation
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The study investigates the intrinsic ionic mechanisms underlying the characteristic metronomic firing activity of RTN neurons, implicating the role of TRPM4 in supporting pacemaker-like firing. TRPM4-dependent oscillatory activity and action potential discharge are modulated by extracellular acidification and serotonin (5-HT).
Brainstem networks that control regular tidal breathing depend on excitatory drive, including from tonically active, CO2/H+-sensitive neurons of the retrotrapezoid nucleus (RTN). Here, we examine intrinsic ionic mechanisms underlying the metronomic firing activity characteristic of RTN neurons. In mouse brainstem slices, large-amplitude membrane potential oscillations are evident in synaptically isolated RTN neurons after blocking action potentials. The voltage-dependent oscillations are abolished by sodium replacement; blocking calciumchannels (primarily L-type); chelating intracellular Ca2+; and inhibiting TRPM4, a Ca2+-dependent cationic channel. Likewise, oscillation voltage waveform currents are sensitive to calcium and TRPM4 channel blockers. Extracellular acidification and serotonin (5-HT) evoke membrane depolarization that augments TRPM4-dependent oscillatory activity and action potential discharge. Finally, inhibition of TRPM4 channels in the RTN of anesthetized mice reduces central respiratory output. These data implicate TRPM4 in a subthreshold oscillation that supports the pacemaker-like firing of RTN neurons required for basal, CO2-stimulated, and state-dependent breathing.
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