Papers by Matthieu Dacher
Journal of Comparative Physiology A
Frontiers in Physiology
In several insects, sex-pheromones are essential for reproduction and reproductive isolation. Phe... more In several insects, sex-pheromones are essential for reproduction and reproductive isolation. Pheromones generally elicit stereotyped behaviors. In moths, these are attraction to conspecific sex-pheromone sources and deterrence for heterospecific sex-pheromone. Contrasting with these innate behaviors, some results in social insects point toward effects of non-sex-pheromones on perception and learning. We report the effects of sex-pheromone pre-exposure on gustatory perception and habituation (a non-associative learning) in male Agrotis ipsilon moths, a non-social insect. We also studied the effect of Z5-decenyl acetate (Z5), a compound of the sex-pheromone of the related species Agrotis segetum. We hypothesized that conspecific sex-pheromone and Z5 would have opposite effects. Pre-exposure to either the conspecific sex-pheromone or Z5 lasted 15 min and was done either immediately or 24 h before the experiments, using their solvent alone (hexane) as control. In a sucrose responsiveness assay, pre-exposure to the conspecific sex-pheromone had no effect on the dose-response curve at either delays. By contrast, Z5 slightly improved sucrose responsiveness 15 min but not 24 h after pre-exposure. Interestingly, the conspecific sex-pheromone and Z5 had time-dependent effects on gustatory habituation: pre-exposing the moths with Z5 hindered learning after immediate but not 24-h pre-exposure, whereas pre-exposure to the conspecific sex-pheromone hindered learning at 24-h but not immediate pre-exposure. They did not have opposite effects. This is the first time a sex-pheromone is reported to affect learning in a non-social insect. The difference in modulation between conspecific sex-pheromone and Z5 suggests that con-and hetero-specific sex-pheromones act on plasticity through different cerebral pathways.
Frontiers in Synaptic Neuroscience
Scientific Reports
Honey bees learn to associate sugars with odorants in controlled laboratory conditions and during... more Honey bees learn to associate sugars with odorants in controlled laboratory conditions and during foraging. The memory of these associations can be impaired after exposure to contaminants such as pesticides. The sub-lethal effects of acaricides such as 5-methyl-2-(propan-2-yl)-phenol (thymol) introduced into colonies to control varroa mites are of particular concern to beekeeping, due to detrimental effects of some acaricides on bees. Here we assess whether various odorant/sugar pairs are identically memorized in a differential appetitive olfactory conditioning experiment and whether this learning is affected by thymol exposure. Responses to odorants in retrieval tests varied according to the sugar they were paired with, a property called congruency. Interestingly, congruency was altered by pre-exposure to some thymol concentrations during retrieval tests, although electroantennography recordings showed it left odorant detection intact. This highlights the importance of taking into account subtle effects such as odor/sugar congruency in the study of the effect of pesticides on non-target insects, in addition to the simpler question of memory impairment.
Chemosphere
Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemic... more Di (2-ethylhexyl) phthalate (DEHP) is recognized in vertebrates as an Endocrine Disrupting Chemical (EDC). DEHP can alter steroid hormones production, development, reproduction and behavior in vertebrates. Only few studies investigated DEHP effects on insects. However, some recent studies on aquatic insects showed that DEHP could also act as an EDC by interfering with the signaling pathways of ecdysteroids, the main hormones involved in the control of insect postembryonic development and physiology. The aim of the study was to investigate (1) the fate of DEHP within a terrestrial insect species by exposing larvae to food containing a wide range of DEHP concentrations and (2) the effects of this chemical on their post-embryonic development and metamorphosis, by using a multi-level approach. DEHP was shown to be present both in larvae and resulting stages, with higher concentrations in chrysalises and adults than in larvae. DEHP concentrations also decreased at the end of the last larval instar, suggesting the metabolic transformation or excretion of this chemical during this time. Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. Metabolic profiles showed that in control insects, the last three days before metamorphosis correspond to a metabolic transition, but with time-dependent changes in treated insects. Interestingly, DEHP treatments also alter both hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. These results confirm that DEHP can alter insect post-embryonic development and metamorphosis, by interfering with ecdysteroid pathways.
Frontiers in Physiology
Adult moths need energy and nutrients for reproducing and obtain them mainly by consuming flower ... more Adult moths need energy and nutrients for reproducing and obtain them mainly by consuming flower nectar (a solution of sugars and other compounds). Gustatory perception gives them information on the plants they feed on. Feeding and food perception are integrated in the proboscis extension response, which occurs when their antennae touch a sugar solution. We took advantage of this reflex to explore moth sugar responsiveness depending on different parameters (i.e., sex, age, satiety, site of presentation, and composition of the solution). We observed that starvation but not age induced higher response rates to sucrose. Presentation of sucrose solutions in a randomized order confirmed that repeated sugar stimulations did not affect the response rate; however, animals were sometimes sensitized to water, indicating sucrose presentation might induce non-associative plasticity. Leg stimulation was much less efficient than antennal stimulation to elicit a response. Quinine prevented and terminated sucrose-elicited proboscis extension. Males but not females responded slightly more to sucrose than to fructose. Animals of either sex rarely reacted to glucose, but curiously, mixtures in which half sucrose or fructose were replaced by glucose elicited the same response rate than sucrose or fructose alone. Fructose synergized the response when mixed with sucrose in male but not female moths. This is consistent with the fact that nectars consumed by moths in nature are mixtures of these three sugars, which suggests an adaptation to nectar perception.
Disciplines : Neurosciences et Biologie du Comportement présentée et soutenue par Matthieu DACHER... more Disciplines : Neurosciences et Biologie du Comportement présentée et soutenue par Matthieu DACHER le 1 er septembre 2005 Remerciements 3 REMERCIEMENTS Il est un bon usage, en thésiennes rédactions : Celui de rendre grâce, en tête de l'escrit, Aux nobles gentilhommes, aux dames pleines d'attentions, A ceux quy par leurs actes, m'amènent à dire mercy. Icelles actions de grâce, iceux remerciements, Ne sont point convenances, encore moins boniments, Mais vray reconnaissance, et justes compliments. Les voicy quy commencent, par maistres du jugement. A vous aussy, ô apidologiques confrères, Je souhaiterai présenter un hommage appuyé : Tous unis, tous ensembles, portant la même bannière, Rassemblés d'un seul coeur, d'Abeilles les écuyers. Cognition animale, voicy noble sujet ! Vous belles damoiselles, vous gentils chevaliers, Dont l'esprit de la beste des recherches est l'objet, Je vous fais mes adieux, nous quy étions alliés. Après toute cette parlure, encrant tout ce papier, Il me faut tous mes proches, remercier également, Par alliance contractée, ou bien par lien du sang, Ou bien même amitié aux fidèles équipiers.
Disciplines : Neurosciences et Biologie du Comportement présentée et soutenue par Matthieu DACHER... more Disciplines : Neurosciences et Biologie du Comportement présentée et soutenue par Matthieu DACHER le 1 er septembre 2005 Remerciements 3 REMERCIEMENTS Il est un bon usage, en thésiennes rédactions : Celui de rendre grâce, en tête de l'escrit, Aux nobles gentilhommes, aux dames pleines d'attentions, A ceux quy par leurs actes, m'amènent à dire mercy. Icelles actions de grâce, iceux remerciements, Ne sont point convenances, encore moins boniments, Mais vray reconnaissance, et justes compliments. Les voicy quy commencent, par maistres du jugement. A vous aussy, ô apidologiques confrères, Je souhaiterai présenter un hommage appuyé : Tous unis, tous ensembles, portant la même bannière, Rassemblés d'un seul coeur, d'Abeilles les écuyers. Cognition animale, voicy noble sujet ! Vous belles damoiselles, vous gentils chevaliers, Dont l'esprit de la beste des recherches est l'objet, Je vous fais mes adieux, nous quy étions alliés. Après toute cette parlure, encrant tout ce papier, Il me faut tous mes proches, remercier également, Par alliance contractée, ou bien par lien du sang, Ou bien même amitié aux fidèles équipiers.
The Journal of Physiology, 2013
• GABAergic synapses onto ventral tegmental area (VTA) dopamine neurons express a bidirectional s... more • GABAergic synapses onto ventral tegmental area (VTA) dopamine neurons express a bidirectional spike timing-dependent plasticity (STDP; both long-term potentiation and long-term depression). • GABAergic synapses in the VTA obey the classical Hebbian learning rules of STDP. • GABAergic STDP in VTA dopamine neurons is expressed postsynaptically. • GABAergic STDP is heterosynaptic and NMDA receptor dependent. • Pairing of pre-and postsynaptic spiking is necessary for induction of GABAergic STDP.
PLoS ONE, 2008
Background: Restrained worker honey bees are a valuable model for studying the behavioral and neu... more Background: Restrained worker honey bees are a valuable model for studying the behavioral and neural bases of olfactory plasticity. The proboscis extension response (PER; the proboscis is the mouthpart of honey bees) is released in response to sucrose stimulation. If sucrose stimulation is preceded one or a few times by an odor (forward pairing), the bee will form a memory for this association, and subsequent presentations of the odor alone are sufficient to elicit the PER. However, backward pairing between the two stimuli (sucrose, then odor) has not been studied to any great extent in bees, although the vertebrate literature indicates that it elicits a form of inhibitory plasticity.
Neuropharmacology, 2011
Opiates are among the most powerful analgesics and pain-relieving agents. However, they are poten... more Opiates are among the most powerful analgesics and pain-relieving agents. However, they are potentially extremely addictive thereby limiting their medical use, making them exceedingly susceptible to abuse and adding to the global drug problem. It is believed that positive memories associated with the pleasurable effects of opiates and negative memories associated with dysphoria during opiate withdrawal contribute to compulsive opiate-seeking behavior characterizing addiction. There is a vast amount of available data regarding the neuroadaptations in response to opiates during opiate tolerance, dependence and withdrawal that contribute to opiate addiction, yet it is still a major challenge to identify the neurobiological adaptations that underlie the hallmarks of opiate addiction such as compulsive drug use, and relapse to drug seeking. Since the discovery of synaptic plasticity as the cellular correlate of learning and memory, strong overlaps between neural and cellular substrates of learning and addiction have been recognized. Consequently, the current notion of addiction supports the idea that aberrant forms of druginduced synaptic plasticity and learning in the brain drive addictive behaviors. Here we discuss current progress on some of the recently identified forms of synaptic plasticity at excitatory and inhibitory synapses in opioid-sensitive areas of the brain that are targeted by opiates and other addictive drugs. The neuroadaptations involved in opiate tolerance, dependence and withdrawal will be re-visited since they share many features with synaptic learning mechanisms.
Neuropharmacology, 2011
Adaptive behaviors often require the learning of appropriate responses to rewarding stimuli, yet ... more Adaptive behaviors often require the learning of appropriate responses to rewarding stimuli, yet aberrant learning processes can lead to serious diseases such as addiction. Dopamine (DA) neurons of the ventral tegmental area (VTA) play an essential role in the treatment of rewarding stimuli, and they exhibit plasticity in response to such stimuli, but also to drugs of abuse. Previously we discovered a form of presynaptic nitric oxide (NO)-mediated long-term potentiation (LTP GABA ) at GABAergic synapses onto VTA DA neurons that is prevented with morphine in vivo 24 h after exposure. Here we investigated whether the same GABAergic synapses are capable of exhibiting long-term depression (LTD in addition to LTP GABA ) and its possible modulation by morphine in vivo. We found that indeed the efficacy of VTA GABAergic synapses can be down-regulated through induction of a novel form of LTD (i.e., LTD GABA ) in response to synaptic stimulation. Paired pulse ratio (PPR) and coefficient of variance (CV) analyses of evoked IPSCs confirmed that this plasticity may be postsynaptic. Consistently, LTD GABA did not involve presynaptic cannabinoid CB 1 receptors (CB 1 Rs). Moreover, NMDAR activation was not necessary for LTD GABA . However, blockade of D 2 dopamine receptors (D 2 R) significantly attenuated LTD GABA proposing a novel synaptic mechanism for the regulation of excitability of DA neurons by endogenous DA and D 2 R activation. Interestingly, 24 h after a single in vivo exposure to morphine, LTD GABA was absent in slices from morphine-treated rats but unaffected in slices from saline-treated rats, confirming a bidirectional impact of morphine on GABAergic synaptic plasticity in the VTA. The control of bidirectional GABAergic plasticity by morphine in the VTA may represent the neural correlates necessary for the addictive properties of opiates.
Behavioral Neuroscience, Jul 1, 2003
Regional brain variations of cytochrome oxidase (CO) staining were analyzed in the honeybee (Apis... more Regional brain variations of cytochrome oxidase (CO) staining were analyzed in the honeybee (Apis mellifera) after olfactory conditioning of the proboscis extension reflex. Identification of brain sites where stimuli converge was done by precise image analysis performed in antennal lobes (AL) and mushroom bodies (MB). In Experiment 1, bees received 5 odorant stimulations that induced a transient decrease of CO activity in the lateral part of the AL. In Experiment 2, bees were trained with 5-trial olfactory conditioning. CO activity transiently increased in the lips of the MB calyces. There was also a delayed increase in the lateral part of the AL. An olfactory stimulus presented alone and an odor paired to a sucrose stimulation are treated by different pathways, including both AL and MB.
Archives of Environmental Contamination and Toxicology, Jun 1, 2008
Acetamiprid and thiamethoxam are insecticides introduced for pest control, but they can also affe... more Acetamiprid and thiamethoxam are insecticides introduced for pest control, but they can also affect nontarget insects such as honeybees. In insects, these neonicotinoid insecticides are known to act on acetylcholine nicotinic receptors but the behavioral effects of low doses are not yet fully understood. The effects of acetamiprid and thiamethoxam were studied after acute sublethal treatment on the behavior of the honeybee (Apis mellifera) under controlled laboratory conditions. The drugs were either administered orally or applied topically on the thorax. After oral consumption acetamiprid increased sensitivity to antennal stimulation by sucrose solutions at doses of 1 lg/bee and impaired long-term retention of olfactory learning at the dose of 0.1 lg/bee. Acetamiprid thoracic application induced no effect in these behavioral assays but increased locomotor activity (0.1 and 0.5 lg/bee) and water-induced proboscis extension reflex (0.1, 0.5, and 1 lg/bee). Unlike acetamiprid, thiamethoxam had no effect on bees' behavior under the conditions used. Our results suggest a particular vulnerability of honeybee behavior to sublethal doses of acetamiprid.
Neurobiol Learn Memory, 2006
Chez les insectes, l'acétamipride et le thiamethoxam sont des néonicotinoïdes qui agissent sur le... more Chez les insectes, l'acétamipride et le thiamethoxam sont des néonicotinoïdes qui agissent sur les récepteurs cholinergiques nicotiniques. Nous avons recherché des effets sublétaux de ces pesticides sur la sensibilité au sucre, sur la motricité et sur la mémoire des abeilles qui ont été contaminées soit par application topique sur le thorax soit par administration orale. À la suite d'une consommation orale d'acétamipride à 1µg/abeille, la sensibilité des abeilles au sucre augmente. L'acétamipride à la dose de 0,1µg/abeille, induit une baisse de la mémoire à long terme. Ces effets ne sont pas observés après application topique d'acétamipride. Par ailleurs, à la dose de 0,1 et 0,5µg/abeille, l'acétamipride augmente l'activité locomotrice et la sensibilité à l'eau.
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Papers by Matthieu Dacher