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Sodium current expression during postnatal development of rat outer hair cells
D Oliver1, P Plinkert, H P Zenner
1Section of Sensory Biophysics, Department of Otolaryngology, University of Tübingen, Röntgenweg 11, Germany.
Pflugers Archiv : European Journal of Physiology
|November 5, 1997
Summary
Immature outer hair cells in newborn rats express voltage-gated sodium channels, crucial for auditory function. These channels diminish significantly by 18 days, suggesting a developmental role in hearing.
Area of Science:
- Neuroscience
- Auditory Physiology
- Cell Biology
Background:
- Outer hair cells (OHCs) are vital for hearing by amplifying sound stimuli.
- The expression and function of ion channels in developing OHCs are not fully understood.
Purpose of the Study:
- To investigate the presence and properties of voltage-gated sodium currents in immature rat outer hair cells.
- To explore the developmental changes and potential physiological role of these currents.
Main Methods:
- Whole-cell patch-clamp recordings were performed on cultured organ of Corti from newborn rats (0-11 days old).
- Voltage-activated sodium currents were characterized by their kinetics, voltage dependence, and sensitivity to pharmacological agents like tetrodotoxin.
- Current-clamp recordings assessed membrane potential and the ability to trigger action potentials.
Main Results:
- A voltage-activated sodium current was detected in 97% of OHCs from 0-9 days old.
- The current exhibited fast activation/inactivation, with specific voltage dependencies and temperature sensitivity.
- Current amplitude peaked around postnatal days 3-7 and significantly decreased by day 18.
- Immature OHCs had membrane potentials capable of generating action potentials under specific conditions.
Conclusions:
- Immature outer hair cells express functional voltage-gated sodium channels, unlike their adult counterparts.
- The developmental expression profile suggests a transient role in early auditory development.
- A potential mismatch between sodium current inactivation and membrane potential in vitro raises questions about their physiological function in vivo.