Differential sensitivity of two insect GABA-gated chloride channels to dieldrin, fipronil and picrotoxinin

Abstract

In the central nervous system of both vertebrates and invertebrates inhibitory neurotransmission is mainly achieved through activation of γ-aminobutyric acid (GABA) receptors. Extensive studies have established the structural and pharmacological properties of vertebrate GABA receptors. Although the vast majority of insect GABA-sensitive responses share some properties with vertebrate GABAA receptors, peculiar pharmacological properties of these receptors led us to think that several GABA-gated chloride channels are present in insects. We describe here the pharmacological properties of two GABA receptor subtypes coupled to a chloride channel on dorsal unpaired median (DUM) neurones of the adult male cockroach. Long applications of GABA induce a large biphasic hyperpolarization, consisting of an initial transient hyperpolarization followed by a slow phase of hyperpolarization that is not quickly desensitized. With GABA, the transient hyperpolarization is sensitive to picrotoxinin, fipronil and dieldrin whereas the slow response is insensitive to these insecticides.When GABA is replaced by muscimol and cis-4-aminocrotonic acid (CACA) a biphasic hyperpolarization consisting of an initial transient hyperpolarization followed by a sustained phase is evoked which is blocked by picrotoxinin and fipronil. Exposure to dieldrin decreases only the early phase of the muscimol and CACA-induced biphasic response, suggesting that two GABA-gated chloride channel receptor subtypes are present in DUM neurones. This study describes, for the first time, a dieldrin resistant component different to the dieldrin-and picrotoxinin-resistant receptor found in several insect species. 

Molecular cloning of a GABA receptor subunit from Laodelphax striatella (Fallén) and patch clamp analysis of the homo‐oligomeric receptors expressed in a Drosophila cell line

“…This is the first report that describes the functional expression of the hemipteran GABA receptor in a cell line. Further efforts will be needed to confirm whether the native insect GABA receptor is a homomer or a heteromer that includes a subunit(s) other than Rdl (Le Corronc et al ., 2002; Buckingham & Sattelle, 2004). However, because the Rdl homo‐oligomer is pharmacologically similar to the native GABA receptor (Buckingham et al ., 1996), our success in the functional expression of a GABA receptor from an agricultural pest presents a unique opportunity to discover new insecticides.…”

Coding of odors by temporal binding within a model network of the locust antennal lobe

“…Since co-localization of GABA receptors with kinetics operating over disparate time scales has been observed in a variety of insect systems (Cayre et al, 1999; Corronc et al, 2002; Barbara et al, 2005; Enell et al, 2007), the assumption that slow and fast receptors have similar distributions within the locust AL seems reasonable.…”

<I>Rdl</I> Gene Polymorphism and Sequence Analysis and Relation to In Vivo Fipronil Susceptibility in Strains of the Cat Flea

“…However, the interaction of dieldrin within the GABAgated ion channel may differ from that of Þpronil (Le Corronc et al 2002, Zhao et al 2003. Furthermore, in addition to targeting the GABA-gated chloride ion channel, Þpronil also has activity at two distinct glutamate-gated chloride ion channels: one desensitizing and the other nondesensitizing, each of which has different ligand sensitivities (Zhao et al 2003(Zhao et al , 2004.…”