High Potassium Treatment Resets the Circadian Oscillator in Xenopus Retinal Photoreceptors

In vertebrate retina, light hyperpolarizes the photoreceptor membrane, and this is an essential cellular signal for vision. Cellular signals responsible for photic entrainment of some circadian oscillators appear to be distinct from those for vision, but it is not known whether changes in photorecep...

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Bibliographic Details
Published in:Journal of biological rhythms 2004-06, Vol.19 (3), p.208-215
Main Authors: Hasegawa, Minoru, Cahill, Gregory M.
Format: Article
Language:English
Subjects:
Animals
Biological Clocks - physiology
Cell culture
Cells, Cultured
Circadian rhythm
Circadian Rhythm - physiology
Circadian rhythms
Depolarization
Dose-Response Relationship, Drug
Entrainment
Male
Melatonin
Melatonin - metabolism
Membrane potential
Oscillators
Photoperiod
Photoreceptor Cells - cytology
Photoreceptor Cells - drug effects
Photoreceptor Cells - metabolism
Photoreceptors
Potassium
Potassium - pharmacology
Retina
Xenopus
Xenopus laevis
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Summary:In vertebrate retina, light hyperpolarizes the photoreceptor membrane, and this is an essential cellular signal for vision. Cellular signals responsible for photic entrainment of some circadian oscillators appear to be distinct from those for vision, but it is not known whether changes in photoreceptor membrane potential play roles in photic entrainment of the photoreceptor circadian oscillator. The authors show that a depolarizing exposure to high potassium resets the circadian oscillator in cultured Xenopus retinal photoreceptor layers. A 4-h pulse of high [K+] (34 mM higher than in normal culture medium) caused phase shifts of the melatonin rhythm. This treatment caused phase delays during the early subjective day and phase advances during the late subjective day. In addition to the phase-shifting effect, high potassium pulses stimulated melatonin release acutely at all times. High [K+] therefore mimicked dark in its effects on oscillator phase and melatonin synthesis. These results suggest that membrane potential may play a role in photic entrainment of the photoreceptor circadian oscillator and in regulation of melatonin release.
ISSN:0748-7304
1552-4531
DOI:10.1177/0748730404264774