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J Neurophysiol 97: 2642-2650, 2007. First published January 31, 2007; doi:10.1152/jn.01234.2006
0022-3077/07 $8.00

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Dorsal Unpaired Median Neurons of Locusta migratoria Express Ivermectin- and Fipronil-Sensitive Glutamate-Gated Chloride Channels

¹Centre of Environmental Sciences, Department of Physiology, and ²Biomedical Research Institute, Hasselt University and Transnationale Universiteit Limburg, Diepenbeek, Belgium; and ³Institute for Integrative Neuroanatomy, Berlin, Germany

Submitted 24 November 2006; accepted in final form 25 January 2007

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 µM fipronil or 100 µM picrotoxin reversibly decreased GluCl-mediated currents by 87 and 39%, respectively. Furthermore, 1 µM ivermectin induced a persistent chloride current, suggesting the expression of ivermectin-sensitive GluCl subunits. A degenerate PCR/RACE strategy was used to clone the full-length L. migratoria LmGlCl subunit. Finally, RT-PCR experiments demonstrated the presence of LmGluCl 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.