Characterization of a transient outward current in a rapidly adapting insect mechanosensory neuron

This paper describes the first voltage-clamp recordings from an arthropod cuticular sensory neuron. In the femoral tactile spine neuron of the cockroach Periplaneta americana, a rapidly activating and inactivating outward current, IA, appeared when the neuron was hyperpolarized for a short period be...

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Bibliographic Details
Published in:Pflügers Archiv 1994-11, Vol.429 (1), p.72-78
Main Authors: Torkkeli, P H, French, A S
Format: Article
Language:English
Subjects:
4-Aminopyridine - pharmacology
Action Potentials - drug effects
Action Potentials - physiology
Animals
Electrophysiology
In Vitro Techniques
Ion Channels - drug effects
Ion Channels - physiology
Kinetics
Mechanoreceptors - drug effects
Mechanoreceptors - physiology
Membrane Potentials - physiology
Microelectrodes
Neurons, Afferent - drug effects
Neurons, Afferent - physiology
Patch-Clamp Techniques
Periplaneta - physiology
Periplaneta americana
Tetrodotoxin - pharmacology
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Summary:This paper describes the first voltage-clamp recordings from an arthropod cuticular sensory neuron. In the femoral tactile spine neuron of the cockroach Periplaneta americana, a rapidly activating and inactivating outward current, IA, appeared when the neuron was hyperpolarized for a short period before a depolarizing test pulse. IA could be separated from the other outward currents using 5 mM 4-aminopyridine (4-AP), which specifically blocked it. Tetraethylammonium (TEA), (50 mM) did not remove IA, but decreased the steady-state outward current by about 50%. The threshold for IA activation was about -75 mV. The minimum activation and inactivation time constants were approximately 0.2 ms and 15 ms, respectively. The voltage dependencies of activation and inactivation were well fit-ted by Boltzmann distributions, giving values of membrane potential at half-maximal activation (V50) equal to -56.5 mV and an equivalent gating charge of n = 3.9 for activation and V50 = -86.7 mV and n = 3.4 for inactivation. In current-clamp recordings, 4-AP reversibly reduced the cell's normal adaptation by lowering the threshold for action potentials, but did not affect the amplitude or duration of single action potentials. These results indicate that IA plays a role in short-term adaptation by opposing membrane depolarization and reducing the spike frequency during maintained stimulation.
ISSN:0031-6768
1432-2013
DOI:10.1007/BF02584032