Skip to main content
Article thumbnail
Location of Repository

Mechanism of Ivermectin Facilitation of Human P2X4 Receptor Channels

By Avi Priel and Shai D. Silberberg

Abstract

Ivermectin (IVM), a widely used antiparasitic agent in human and veterinary medicine, was recently shown to augment macroscopic currents through rat P2X4 receptor channels (Khakh, B.S., W.R. Proctor, T.V. Dunwiddie, C. Labarca, and H.A. Lester. 1999. J. Neurosci. 19:7289–7299.). In the present study, the effects of IVM on the human P2X4 (hP2X4) receptor channel stably transfected in HEK293 cells were investigated by recording membrane currents using the patch clamp technique. In whole-cell recordings, IVM (≤10 μM) applied from outside the cell (but not from inside) increased the maximum current activated by ATP, and slowed the rate of current deactivation. These two phenomena likely result from the binding of IVM to separate sites. A higher affinity site (EC50 0.25 μM) increased the maximal current activated by saturating concentrations of ATP without significantly changing the rate of current deactivation or the EC50 and Hill slope of the ATP concentration-response relationship. A lower affinity site (EC50 2 μM) slowed the rate of current deactivation, and increased the apparent affinity for ATP. In cell-attached patch recordings, P2X4 receptor channels exhibited complex kinetics, with multiple components in both the open and shut distributions. IVM (0.3 μM) increased the number of openings per burst, without significantly changing the mean open or mean shut time within a burst. At higher concentrations (1.5 μM) of IVM, two additional open time components of long duration were observed that gave rise to long-lasting bursts of channel activity. Together, the results suggest that the binding of IVM to the higher affinity site increases current amplitude by reducing channel desensitization, whereas the binding of IVM to the lower affinity site slows the deactivation of the current predominantly by stabilizing the open conformation of the channel

Topics: Article
Publisher: The Rockefeller University Press
OAI identifier: oai:pubmedcentral.nih.gov:2217454
Provided by: PubMed Central
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://www.pubmedcentral.nih.g... (external link)
  • Suggested articles

    Citations

    1. (1992). A potassium current activated by lemakalim and metabolic inhibition in rabbit mesenteric artery. Pflugers Arch.
    2. (1991). Accounting for the Ca2 -dependent kinetics of single large-conductance Ca2 -activated K channels in rat skeletal muscle.
    3. (2000). Activation of rat recombinant 1, 2, 2S GABAA receptor by the insecticide ivermectin.
    4. (1999). Allosteric control of gating and kinetics at P2X4 receptor channels.
    5. (2000). Anticonvulsant and adverse effects of avermectin analogs in mice are mediated through the -aminobutyric acidA receptor.
    6. (1997). avr-15 encodes a chloride channel subunit that mediates inhibitory glutamatergic neurotransmission and ivermectin sensitivity in Caenorhabditis elegans.
    7. (2000). Block by extracellular Mg2 of single human purinergic P2X4 receptor channels expressed in human embryonic kidney cells.
    8. (1997). Characterization of recombinant human P2X4 receptor reveals pharmacological differences to the rat ho-293 Priel and Silberberg mologue.
    9. (1994). Cloning of an avermectinsensitive glutamate-gated chloride channel from Caenorhabditis elegans.
    10. (1999). Contribution of individual subunits to the multimeric P2X2 receptor: estimates based on methanethiosulfonate block at T336C.
    11. (1986). Correcting single channel data for missed events.
    12. (1987). Data transformations for improved display and fitting of single-channel dwell time histograms.
    13. (1987). Effect of avermectin B1a on chick neuronal -aminobutyrate receptor channels expressed in Xenopus oocytes.
    14. (1994). Effect of ivermectin on -aminobutyric acid-induced chloride currents in mouse hippocampal embryonic neurones.
    15. (1997). Genetic and biochemical evidence for a novel avermectin-sensitive chloride channel in Caenorhabditis elegans. Isolation and characterization.
    16. (1996). Identification of a Drosophila melanogaster glutamate-gated chloride channel sensitive to the antiparasitic agent avermectin.
    17. (2002). Identification of two novel Drosophila melanogaster histamine-gated chloride channel subunits expressed in the eye.
    18. (1981). Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch.
    19. (1999). Ion permeation and block of P2X2 purinoceptors: single channel recordings.
    20. (2001). Ivermectin excretion by isolated functionally intact brain endothelial capillaries.
    21. (2001). Ivermectin, an unconventional agonist of the glycine receptor chloride channel.
    22. (1998). Ivermectin: a positive allosteric effector of the 7 neuronal nicotinic acetylcholine receptor.
    23. (2000). Ivermectin: an assessment of its pharmacology, microbiology and safety.
    24. (1988). Kinetic states and modes of single large-conductance calcium-activated potassium channels in cultured rat skeletal muscle.
    25. (2002). Molecular physiology of P2X receptors.
    26. (1988). Muscarinic activation of ionic currents measured by a new whole-cell recording method.
    27. (1997). P-glycoprotein deficiency in a subpopulation of CF-1 mice enhances avermectin-induced neurotoxicity.
    28. (1998). P2X1 and P2X3 receptors form stable trimers: a novel structural motif of ligand-gated ion channels.
    29. (2003). P2X4, P2Y1 and P2Y2 receptors on rat alveolar macrophages.
    30. (2002). Safety, tolerability, and pharmacokinetics of escalating high doses of ivermectin in healthy adult subjects.
    31. (1996). Single channel properties of ATP-gated cation channels (P2X receptors) heterologously expressed in Chinese hamster ovary cells.
    32. (1995). Single-Channel Recording, 2nd edition.
    33. (1993). Stretch-activated channels in airway epithelial cells.
    34. (2002). Study of the nematode putative GABA type-A receptor subunits: evidence for modulation by ivermectin.
    35. (2001). The biochemical basis of anthelmintic action and resistance.
    36. (2000). The genetics of ivermectin resistance in Caenorhabditis elegans.
    37. (1989). The insecticide avermectin B1a activates a chloride channel in crayfish muscle membrane.
    38. (2003). Tissue distribution of P2X4 receptors studied with an ectodomain antibody. Cell Tissue Res.

    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.