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Proton-activated currents in chick spinal motoneurons
H Hatt1, J L Rosenheimer, D O Smith
1Physiologisches Institut der Technischen Universität München, Germany.
Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology
|October 1, 1995
Summary
Transient decreases in extracellular pH activate large inward currents in embryonic chick motoneurons. These proton-activated currents inactivate rapidly and reactivate slowly, potentially impacting neuronal function during pathological conditions.
Area of Science:
- Neuroscience
- Electrophysiology
- Ion Channel Physiology
Background:
- Extracellular pH fluctuations can influence neuronal excitability.
- Proton-activated channels play a role in neuronal signaling.
Purpose of the Study:
- To characterize proton-activated currents in embryonic chick motoneurons.
- To investigate the properties of these currents, including activation, inactivation, and ion selectivity.
Main Methods:
- Patch-clamp recordings from embryonic chick motoneurons.
- Rapid application of protons to alter extracellular pH.
- Single-channel recordings to analyze channel kinetics and conductance.
Main Results:
- Proton application evoked large, inactivating inward currents.
- Half-maximal activation (EC50) occurred at pH 6.8.
- Single-channel analysis revealed fast activation, specific open/closed times, and a conductance of 22 pS at pH 6.5.
- Currents were modulated by Ni2+ and Ca2+ concentrations.
- Inactivation was pH-dependent but not voltage-dependent, with slow reactivation.
- Proton- and glutamate-activated currents showed summation.
Conclusions:
- Transient extracellular acidity activates inward currents in motoneurons.
- These currents exhibit rapid inactivation and slow reactivation.
- Such currents may be relevant in pathological states affecting extracellular pH.