Differential Phase Arrangement of Cellular Clocks along the Tonotopic Axis of the Mouse Cochlea Ex Vivo.
Level 5 - mechanism / opinion, no new human data
Ex vivo animal bench research
PubMed 28823676 · doi:10.1016/j.cub.2017.07.019
What was done
Researchers tracked PER2::LUC bioluminescence in real time using mouse cochlear explants and isolated cochlear subregions ex vivo. They analyzed the spatial organization and phase relationships of cellular circadian oscillators across the apical, middle, and basal turns (the tonotopic axis) and evaluated rhythm disruption following pharmacological exposure to TEA (potassium channel blocker), BAPTA (extracellular calcium chelator), TTX (sodium channel blocker), and carbenoxolone (CBX, gap junction blocker).
What was found
Hair cells and spiral ganglion neurons exhibited cell-autonomous, self-sustained oscillations. Rhythms initiated in the apical (low-frequency) region and traveled toward the base (high-frequency region), displaying a 3-hour phase difference between apical and middle regions. Rhythms were disrupted by TEA and BAPTA, whereas TTX and CBX had no effect on cochlear rhythmicity.
Why it matters
This study provides evidence of a spatiotemporal phase gradient of cellular circadian clocks mapped along the tonotopic axis in a peripheral sensory organ. It also identifies that potassium and calcium channels, rather than action potentials or gap junctions, are required to sustain these cochlear oscillations.
Limits
The study was conducted entirely ex vivo in mouse tissue; exact sample sizes (number of animals or explants), effect sizes, and statistical variance were omitted from the abstract, and findings may not directly mirror intact in vivo mammalian auditory physiology.
Cited by
- supports The inner ear possesses its own intrinsic circadian rhythm, which can influence the efficacy of certain drugs depending on the time of day they are administered.