Cys-loop ligand-gated chloride channels in dorsal unpaired median neurons of Locusta migratoria.
In insects, inhibitory neurotransmission is generally associated with members of the cys-loop ligand-gated anion channels, such as the glutamate-gated chloride channel (GluCl), the GABA-gated chloride channels (GABACl), and the histamine-gated chloride channels (HisCl). These ionotropic receptors are considered established target sites for the development of insecticides, and therefore it is necessary to obtain a better insight in their distribution, structure, and functional properties. Here, by combining electrophysiology and molecular biology techniques, we identified and characterized GluCl, GABACl, and HisCl in dorsal unpaired median (DUM) neurons of Locust migratoria. In whole cell patch-clamp recordings, application of glutamate, GABA, or histamine induced rapidly activating ionic currents. GluCls were sensitive to ibotenic acid and blocked by picrotoxin and fipronil. The pharmacological profile of the L. migratoria GABACl fitted neither the vertebrate GABA(A) nor GABA(C) receptor and was similar to the properties of the cloned Drosophila melanogaster GABA receptor subunit (Rdl). The expression of Rdl-like subunit-containing GABA receptors was shown at the molecular level using RT-PCR. Sequencing analysis indicated that the orthologous GABACl of D. melanogaster CG10357-A is expressed in DUM neurons of L. migratoria. Histamine-induced currents exhibited a fast onset and desensitized completely on continuous application of histamine. In conclusion, within the DUM neurons of L. migratoria, we identified three different cys-loop ligand-gated anion channels that use GABA, glutamate, or histamine as their neurotransmitter.
Janssen
Daniel
D
Centre of Environmental Sciences, Department of Physiology, Hasselt University and Transnationale Universiteit Limburg, Agoralaan, Diepenbeek, Belgium. daniel.janssen@uhasselt.be
Derst
Christian
C
Rigo
Jean-Michel
JM
Van Kerkhove
Emmy
E
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006632:Histamine / Q000378:metabolism; D066298:In Vitro Techniques; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D048188:Locusta migratoria; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018118:Chloride Channels; D019476:Insect Proteins; C109777:glutamate-gated chloride channels; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D006632:Histamine