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Cellular analysis of a molluscan retinal biological clock
1NSF Science and Technology Center for Biological Timing, University of Virginia, Charlottesville 22901, USA.
Ciba Foundation Symposium
|January 1, 1995
Summary
Individual neurons in the mollusc Bulla gouldiana act as circadian pacemakers, showing rhythmic changes in membrane conductance. This discovery reveals the cellular basis of circadian rhythms in the optic nerve.
Area of Science:
- Neuroscience
- Chronobiology
- Cellular Biology
Background:
- The eye of Bulla gouldiana exhibits a circadian rhythm in optic nerve impulse frequency.
- This rhythm is generated by basal retinal neurons, which are electrically coupled and fire action potentials synchronously.
Purpose of the Study:
- To investigate whether individual basal retinal neurons can generate circadian rhythms independently.
- To elucidate the cellular mechanisms underlying circadian rhythm generation in these neurons.
Main Methods:
- Intracellular recordings from basal retinal neurons in situ and in culture.
- Analysis of membrane potential and conductance rhythms.
- Investigation of the role of transmembrane ionic fluxes, transcription, and translation.
Main Results:
- Basal retinal neurons display circadian rhythms in membrane potential, modulated by changes in membrane conductance.
- Individual basal retinal neurons in culture maintain circadian conductance rhythms when isolated.
- Transmembrane calcium (Ca2+) flux is critical for entrainment, while other ionic fluxes are not involved in rhythm generation.
Conclusions:
- Individual basal retinal neurons can function as autonomous circadian pacemakers.
- Circadian rhythmicity in these neurons involves transcriptional and translational processes.
- The findings provide direct evidence for single-cell circadian pacemaking in a neural circuit.