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Chaffiol A.,Ohio State University | Kropf J.,University of Würzburg | Barrozo R.B.,University of Buenos Aires | Gadenne C.,CNRS Receptors and Membrane Ion Channels Laboratory | And 2 more authors.
Journal of Experimental Biology | Year: 2012

Male moths are confronted with complex odour mixtures in a natural environment when flying towards a female-emitted sex pheromone source. Whereas synergistic effects of sex pheromones and plant odours have been observed at the behavioural level, most investigations at the peripheral level have shown an inhibition of pheromone responses by plant volatiles, suggesting a potential role of the central nervous system in reshaping the peripheral information. We thus investigated the interactions between sex pheromone and a behaviourally active plant volatile, heptanal, and their effects on responses of neurons in the pheromone-processing centre of the antennal lobe, the macroglomerular complex, in the moth Agrotis ipsilon. Our results show that most of these pheromone-sensitive neurons responded to the plant odour. Most neurons responded to the pheromone with a multiphasic pattern and were anatomically identified as projection neurons. They responded either with excitation or pure inhibition to heptanal, and the response to the mixture pheromone + heptanal was generally weaker than to the pheromone alone, showing a suppressive effect of heptanal. However, these neurons responded with a better resolution to pulsed stimuli. The other neurons with either purely excitatory or inhibitory responses to all three stimuli did not exhibit significant differences in responses between stimuli. Although the suppression of the pheromone responses in AL neurons by the plant odour is counterintuitive at first glance, the observed better resolution of pulsed stimuli is probably more important than high sensitivity to the localization of a calling female. © 2012. Published by The Company of Biologists Ltd.

Anderson P.,Swedish University of Agricultural Sciences | Anton S.,CNRS Receptors and Membrane Ion Channels Laboratory
Plant, Cell and Environment | Year: 2014

Plant volatiles are important cues for many herbivorous insects when choosing a suitable host plant and finding a mating partner. An appropriate behavioural response to sensory cues from plants and other insects is crucial for survival and fitness. As the natural environment can show both large spatial and temporal variability, herbivores may need to show behavioural plasticity to the available cues. By using earlier experiences, insects can adapt to local variation of resources. Experience is well known to affect sensory-guided behaviour in parasitoids and social insects, but there is also increasing evidence that it influences host plant choice and the probability of finding a mating partner in herbivorous insects. In this review, we will focus upon behavioural changes in holometabolous insect herbivores during host plant choice and localization of mating partners, modulated by experience to sensory cues. The experience can be acquired during both the larval and the adult stage and can influence later responses to plant volatiles and other sensory cues not only within the developmental stage but also after metamorphosis. Furthermore, we will address the neurophysiological mechanisms underlying the experience-dependent behavioural adaptations and discuss ecological and evolutionary aspects of insect behavioural plasticity based upon experience. © 2014 John Wiley & Sons Ltd.

Thany S.H.,CNRS Receptors and Membrane Ion Channels Laboratory
Advances in Experimental Medicine and Biology | Year: 2010

Insect nicotinic acetylcholine receptors have been objects of attention since the discovery of neonicotinoid insecticides. Mutagenesis studies have revealed that, although the detailed subunit composition of insect nicotinic acetylcholine receptors subtypes eludes us, the framework provided by mutagenesis analysis makes a picture of the subunits involved in the ligand binding and channel properties. In fact, many residues that line the channel or bind to the ligand seemed to be strongly conserved in particular in the N-terminal extracellular region and the second transmembrane domain which constitutes the ion-conducting pathway supporting the flux of ions as well as their discrimination. In fact, the positions are carried by loops B and C, respectively, which contain amino acids directly contributing to the acetylcholine binding site. Mutation of these residues accounts for insect resistance to neonicotinoid insecticides such as imidacloprid or a loss of specific binding. The discovery of the same mutation at homologous residues in different insect species or its conservation raises the intriguing question of whether a single mutation is essential to generate a resistance phenotype or whether some subunit confer insensitivity to ligand. Consequently, recent finding using information from Torpedo marmorata α1 subunit and soluble Aplysia californica and Lymnae stagnalis acetylcholine binding proteins from crystallization suggest that insect nAChR subunits had contributing amino acids in the agonist site structure which participate to affinity and pharmacological properties of these receptors. These new range of data greatly facilitate the understanding of toxin-nAChR interactions and the neonicotinoid binding and selectivity. © 2010 Landes Bioscience and Springer Science+Business Media.

Gadenne C.,CNRS Receptors and Membrane Ion Channels Laboratory | Barrozo R.B.,University of Buenos Aires | Anton S.,CNRS Receptors and Membrane Ion Channels Laboratory
Annual Review of Entomology | Year: 2016

In insects, olfaction plays a crucial role in many behavioral contexts, such as locating food, sexual partners, and oviposition sites. To successfully perform such behaviors, insects must respond to chemical stimuli at the right moment. Insects modulate their olfactory system according to their physiological state upon interaction with their environment. Here, we review the plasticity of behavioral responses to different odor types according to age, feeding state, circadian rhythm, and mating status. We also summarize what is known about the underlying neural and endocrinological mechanisms, from peripheral detection to central nervous integration, and cover neuromodulation from the molecular to the behavioral level. We describe forms of olfactory plasticity that have contributed to the evolutionary success of insects and have provided them with remarkable tools to adapt to their ever-changing environment. © Copyright 2016 by Annual Reviews. All rights reserved.

Demares F.,Toulouse 1 University Capitole | Raymond V.,CNRS Receptors and Membrane Ion Channels Laboratory | Armengaud C.,Toulouse 1 University Capitole
Insect Biochemistry and Molecular Biology | Year: 2013

Due to its specificity to invertebrate species, glutamate-gated chloride channels (GluCls) are the target sites of antiparasitic agents and insecticides, e.g. ivermectin and fipronil, respectively. In nematodes and insects, the GluCls diversity is broadened by alternative splicing. GluCl subunits have been characterized according to their sensitivity to drugs, and to their anatomical localization. In the honeybee, the GluCl gene can encode different alpha subunits due to alternative splicing of exon 3. We examined mRNA expression in brain parts and we confirmed the existence of two GluCl variants with RT-PCR, Amel_GluCl A and Amel_GluCl B. Surprisingly, a mixed isoform not yet described in insect was obtained, we called it Amel_GluCl C. We determined precise immunolocalization of peptide sequence corresponding to Amel_GluCl A and Amel_GluCl B in the honeybee brain. Amel_GluCl A is mainly located in neuropils, whereas Amel_GluCl B is mostly expressed in cell bodies. Both proteins can also be co-localized. According to their anatomical localization, different GluCl variants might be involved in olfactory and visual modalities and in learning and memory. © 2012 Elsevier Ltd.

Thany S.H.,CNRS Receptors and Membrane Ion Channels Laboratory | Tricoire-Leignel H.,CNRS Receptors and Membrane Ion Channels Laboratory
Current Neuropharmacology | Year: 2011

Acetylcholine (ACh) is probably the oldest signalling neurotransmitter which appeared in evolution before the nervous system. It is present in bacteria, algae, protozoa and plants. In insects and mammals it is involved in cell-to-cell communications in various neuronal and non-neuronal tissues. The discovery of nicotinic acetylcholine receptors (nAChRs) as the main receptors involved in rapid cholinergic neurotransmission has helped to understand the role of ACh at synaptic level. Recently, several lines of evidence have indicated that extrasynaptically expressed nAChRs display distinct pharmacological properties from the ones expressed at synaptic level. The role of both nAChRs at insect extrasynaptic and/or synaptic levels has been underestimated due to the lack of pharmacological tools to identify different nicotinic receptor subtypes. In the present review, we summarize recent electrophysiological and pharmacological studies on the extrasynaptic and synaptic differences between insect and mammalian nAChR subtypes and we discuss on the pharmacological impact of several drugs such as neonicotinoid insecticides targeting these receptors. In fact, nAChRs are involved in a wide range of pathophysiological processes such as epilepsy, pain and a wide range of neurodegenerative and psychiatric disorders. In addition, they are the target sites of neonicotinoid insecticides which are known to act as nicotinic agonists causing severe poisoning in insects and mammals. © 2011 Bentham Science Publishers.

Thany S.H.,CNRS Receptors and Membrane Ion Channels Laboratory
Advances in Experimental Medicine and Biology | Year: 2010

The use of neonicotinoid insecticides has grown considerably since their introduction in 1990s. They are used extensively for the control of agriculturally important crop pests and also in the control of cat and dog fleas. Imidacloprid exploited through an elaborated structural and substituent optimization of nithiazine was launched to market in 1990. The selectivity of neonicotinoid compounds for insect species has been attributed to their binding on nicotinic acetylcholine receptors in which the negatively charged nitro- or cyano-groups of neonicotinoid compounds interact with a cationic subsite within insect nicotinic acetylcholine receptors. The first example of a pest evolving resistance to field use of neonicotinoids was Bemisia tabaci. Resistance to neonicotinoids can arise either through nAChR subtypes expression, detoxification mechanisms and/or structural alterations of target-site proteins. Consequently, a number of derivatives and analogues of imidacloprid have been generated to date. In 1992, a new neonicotinoid using acetylcholine as the lead compound has been found. This was dinotefuran, which has a characteristic tetrahydro-3-furylmethyl group instead of the pyridine-like rings of others neonicotinoids. © 2010 Landes Bioscience and Springer Science+Business Media.

Thany S.H.,CNRS Receptors and Membrane Ion Channels Laboratory
Advances in Experimental Medicine and Biology | Year: 2010

The existence of several nicotinic acetylcholine receptor genes in insects suggests that many nicotinic receptor subtypes are present, but the identification and characterization of these subtypes in native neurons has been limited. Their pharmacological properties came from electrophysiological studies in which variations in the sensitivity of insect neurons were correlated with time course, current amplitudes, desensitization rates occurring in varying proportions in different cells. Thus pressure application of agonists on cultured cells induced inward currents showing that acetylcholine and nicotine were partial agonists of some cells with a lower efficacy while they were full agonists in other neurons. The variation in kinetics appeared to be due to differential expression of distinct nicotinic receptor subtypes as corroborated by the blocking activity induced by antagonists. In fact, the alpha-bungarotoxin-sensitive nicotinic receptor subtypes described as homomeric could be also heteromeric receptors. Interestingly, some receptors mediating nicotinic responses have been termed 'mixed' receptors because they were blocked by a range of nicotinic and muscarinic antagonists. Following electrophysiological studies, it has been also demonstrated that insect nicotinic receptors were modulated by Ca2+ pathways. Ca2+ permeability through insect nicotinic receptors, voltage-gated Ca2+ channels or released from intracellular stores represents an important indication of insect native nicotinic acetylcholine receptor modulation. The Ca2+ flow may trigger a variety of cytosolic Ca2+ pathways underlying many cellular processes such Calmodulin kinase, PKA and PKC. Most of the studies suggested that the effect of phosphorylation mechanism was dependent on the receptor subtype. © 2010 Landes Bioscience and Springer Science+Business Media.

Thany S.H.,CNRS Receptors and Membrane Ion Channels Laboratory
Advances in Experimental Medicine and Biology | Year: 2010

A major criteria initially used to localize cholinergic neuronal elements in nervous systems tissues that involve acetylcholine (ACh) as neurotransmitter is mainly based on immunochemical studies using choline acetyltransferase (ChAT), an enzyme which catalyzes ACh biosynthesis and the ACh degradative enzyme named acetylcholinesterase (AChE). Immunochemical studies using anti-ChAT monoclonal antibody have allowed the identification of neuronal processes and few types of cell somata that contain ChAT protein. In situ hybridization using cRNA probes to ChAT or AChE messenger RNA have brought new approaches to further identify cell bodies transcribing the ChAT or AChE genes. Combined application of all these techniques reveals a widespread expression of ChAT and AChE activities in the insect central nervous system and peripheral sensory neurons which implicates ACh as a key neurotransmitter. The discovery of the snake toxin alpha-bungatoxin has helped to identify nicotinic acetylcholine receptors (nAChRs). In fact, nicotine when applied to insect neurons, resulted in the generation of an inward current through the activation of nicotinic receptors which were blocked by alpha-bungarotoxin. Thus, insect nAChRs have been divided into two categories, sensitive and insensitive to this snake toxin. Up to now, the recent characterization and distribution pattern of insect nAChR subunits and the biochemical evidence that the insect central nervous system contains different classes of cholinergic receptors indicated that ACh is involved in several sensory pathways. © 2010 Landes Bioscience and Springer Science+Business Media.

Lavialle-Defaix C.,CNRS Receptors and Membrane Ion Channels Laboratory | Moignot B.,CNRS Receptors and Membrane Ion Channels Laboratory | Legros C.,CNRS Receptors and Membrane Ion Channels Laboratory | Lapied B.,CNRS Receptors and Membrane Ion Channels Laboratory
Journal of Pharmacology and Experimental Therapeutics | Year: 2010

Decarbomethoxylated JW062 (DCJW), the active component of the oxadiazine insecticide (S)-methyl 7-chloro-2,5-dihydro-2-[[(methoxycarbonyl)[4- (trifluoromethoxy)phenyl] amino]carbonyl] indeno[1,2-e][1,3,4]oxadiazine-4a(3H)- carboxylate (DPX-JW062) (indoxacarb), was tested on 2 inward voltage-dependent sodium currents (named INa1 and INa2) expressed in short-term cultured dorsal unpaired median neurons of the cockroach Periplaneta americana. Under whole-cell voltage-clamp conditions, application of DCJW resulted in a biphasic dose-dependent inhibition of the global sodium current amplitude illustrating the differing sensitivity of sodium channels to DCJW. INa2 was less sensitive to DCJW [half-maximal inhibitory concentration (IC50) = 1.6 μM] compared with INa1 (IC50 = 1.7 nM). Although a previous study demonstrated that INa1 was regulated by the cAMP/protein kinase A cascade, we showed that INa2 was mainly regulated in an opposite way by the activation of calcium-calmodulin-dependent protein phosphatase 2B (PP2B) and calcium-calmodulin-dependent protein kinase II (CaM-kinase II). Furthermore, we demonstrated that activation of CaM-kinase II by intracellular calcium via the calcium-calmodulin complex affected the sensitivity of INa2 channels to DCJW. By increasing the intracellular calcium concentration and/or using 1,2-bis(oaminophenoxy) ethane-N,N,N′,N′-tetraacetic acid (BAPTA) (a calcium chelator), N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide hydrochloride (W7) (a calmodulin inhibitor), cyclosporine A (a PP2B inhibitor), and 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62) (a CaM-kinase II inhibitor), we revealed that activation of CaM-kinase II was involved in the modulation of the voltage dependence of steady-state inactivation and that the CaM-kinase II pathway activated by elevation of the intracellular calcium concentration might render INa2 channels approximately 3000-fold more sensitive to DCJW. These results indicated that manipulating specific intracellular signaling pathways involved in the regulation of sodium channels might have fundamental consequences for the sensitivity of insects to insecticides. This finding reveals an exciting research area that could lead to improvement in the efficiency of insecticides. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics.

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