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Mechanism of Cl- sensitivity in internal ion receptors of the leech; an inward current gated off by Cl- in the nephridial nerve cells

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Summary

The nephridial nerve cells of the leech, Hirudo medicinalis, 34 sensory cells, each associated with one nephridium, are sensitive to changes in extracellular Cl- concentration, an important factor in ion homeostasis. Using single-electrode current- and voltage clamp and ion substitution techniques, the specificity and mechanism of Cl- sensitivity of the nephridial nerve cell was studied in isolated preparations. Increase of the normally low external Cl- concentration leads to immediate and sustained hyperpolarization, decrease of the frequency of bursts and decrease of membrane conductance. The response is halogen specific: Cl- can be replaced by Br−, but not by organic mono- or divalent anions or inorganic divalent anions.

At physiological Cl- concentrations (36mM extra-cellular Cl-), the nephridial nerve cell has a high resting conductance for Cl- and the membrane potential is governed by Cl-. In high extracellular Cl- concentrations (110–130 mM), membrane conductance is low, most likely due to the gating off of Cl- channels. Under these conditions, membrane potential is dominated by the K+ distribution and the nephridial nerve cell hyperpolarizes towards EK.

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Abbreviations

NNC :

nephridial nerve cell

V m :

membrane potential

E Cl(k) :

equilibrium potential for Cl (K)

IV-curve :

current-voltage relationship

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Authors and Affiliations

  1. Fakultät für Biologie, Universität Konstanz, Postfach 5560, W-7750, Konstanz, Federal Republic of Germany

    A. Wenning

  2. Department of Biology, Emory University, 30322, Atlanta, GA, USA

    R. L. Calabrese

Authors
  1. A. Wenning
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  2. R. L. Calabrese
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Wenning, A., Calabrese, R.L. Mechanism of Cl- sensitivity in internal ion receptors of the leech; an inward current gated off by Cl- in the nephridial nerve cells. J Comp Physiol A 168, 53–61 (1991). https://doi.org/10.1007/BF00217103

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  • DOI: https://doi.org/10.1007/BF00217103

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