Dorsal unpaired median neurons of locusta migratoria express ivermectin- and fipronil-sensitive glutamate-gated chloride channels.
Together with type A GABA and strychnine-sensitive glycine receptors, glutamate-gated chloride channels (GluCl) are members of the Cys-loop family of ionotropic receptors, which mediate fast inhibitory neurotransmission. To date, GluCls are found in invertebrates only and therefore represent potential specific targets for insecticides, such as ivermectin and fipronil. In this study, we identified the functional expression of GluCls in dorsal unpaired median (DUM) neurons of the metathoracic ganglion of Locusta migratoria using electrophysiological and molecular biological techniques. In whole cell patch-clamped DUM neurons, glutamate-induced changes in both their membrane potentials (current-clamp) and currents (voltage-clamp) were dependent on the chloride equilibrium potential. On continuous application of glutamate, the glutamate-elicited current response became rapidly and completely desensitized. Application of glutamate in the presence of 10 microM fipronil or 100 microM picrotoxin reversibly decreased GluCl-mediated currents by 87 and 39%, respectively. Furthermore, 1 microM ivermectin induced a persistent chloride current, suggesting the expression of ivermectin-sensitive GluCl alpha subunits. A degenerate PCR/RACE strategy was used to clone the full-length L. migratoria LmGlClalpha subunit. Finally, RT-PCR experiments demonstrated the presence of LmGluClalpha transcripts in locust DUM neurons. Our results provide the first direct evidence of a functional ivermectin-sensitive GluCl channel on the cell surface of DUM neurons of L. migratoria.
Janssen
Daniel
D
Centre of Environmental Sciences, Department of Physiology, Hasselt University and Transnationale Universiteit Limburg, Agoralaan, Diepenbeek, 3590, Belgium. daniel.janssen@uhasselt.be
Derst
Christian
C
Buckinx
Roeland
R
Van den Eynden
Jimmy
J
Rigo
Jean-Michel
JM
Van Kerkhove
Emmy
E
D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D003627:Data Interpretation, Statistical; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects*; D007559:Ivermectin / Q000494:pharmacology*; D007700:Kinetics; D048188:Locusta migratoria / Q000502:physiology*; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011720:Pyrazoles / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018118:Chloride Channels; D018076:DNA, Complementary; D007306:Insecticides; D011720:Pyrazoles; D018698:Glutamic Acid; D007559:Ivermectin; C082360:fipronil