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Key points 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., Abstract Persistent changes in excitatory and inhibitory synaptic strengths to the ventral tegmental area (VTA) dopamine (DA) neurons in response to addictive drugs may underlie the transition from casual to compulsive drug use. While an enormous amount of work has been done in the area of glutamatergic plasticity of the VTA, little is known regarding the learning rules governing GABAergic plasticity in the VTA. Spike timing-dependent plasticity, STDP, has attracted considerable attention primarily due to its potential roles in processing and storage of information in the brain and there is emerging evidence for the existence of STDP at inhibitory synapses. We therefore used whole-cell recordings in rat midbrain slices to investigate whether near-coincident pre- and postsynaptic firing induces a lasting change in synaptic efficacy of VTA GABAergic synapses. We found that a Hebbian form of STDP including long-term potentiation (LTP) and long-term depression (LTD) can be induced at GABAergic synapses onto VTA DA neurons and relies on the precise temporal order of pre- and postsynaptic spiking. Importantly, GABAergic STDP is heterosynaptic (NMDA receptor dependent): triggered by correlated activities of the presynaptic glutamatergic input and postsynaptic DA cells. GABAergic STDP is postsynaptic and has an associative component since pre- or postsynaptic spiking per se did not induce STDP. STDP of GABAergic synapses in the VTA provides physiologically relevant forms of inhibitory plasticity that may underlie natural reinforcement of reward-related behaviours. Moreover, this form of inhibitory plasticity may mediate some of the reinforcing, aversive and addictive properties of drugs of abuse. [ABSTRACT FROM AUTHOR]

The postsynaptic scaffolding A-kinase anchoring protein 79/150 (AKAP79/150) signaling complex regulates excitatory synaptic trans-mission and strength through tethering protein kinase A (PKA), PKC, and calcineurin (CaN) to the postsynaptic densities of neurons (Sanderson and Dell'Acqua, 2011), but its role in inhibitory synaptic transmission and plasticity is unknown. Using immunofluorescence and whole-cell patch-clamp recording in rat midbrain slices, we show that activation of postsynaptic DM2-like family of dopamine (DA) receptor in the ventral tegmental area (VTA) induces long-term depression (LTD) of GABAergic synapses on DA neurons through an inositol triphosphate receptor-mediated local rise in postsynaptic Ca2+ and CaN activation accompanied by PKA inhibition, which requires AKAP150 as a bridging signaling molecule. Our data also illuminate a requirement for a clathrin-mediated internalization of GABAA receptors in expression of LTDGABA. Moreover, disruption of AKAP-PKA anchoring does not affect glutamatergic synapses onto DA neurons, suggesting that the PKA-AKAP-CaN complex is uniquely situated at GABAA receptor synapses in VTA DA neurons to regulate plasticity associated with GABAA receptors. Drug-induced modulation of GABAergic plasticity in the VTA through such novel signaling mechanisms has the potential to persistently alter the output of individual DA neurons and of the VTA, which may contribute to the reinforcing or addictive properties of drugs of abuse. [ABSTRACT FROM AUTHOR]

Abstract: 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 (LTPGABA) 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 LTPGABA) 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., LTDGABA) 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, LTDGABA did not involve presynaptic cannabinoid CB1receptors (CB1Rs). Moreover, NMDAR activation was not necessary for LTDGABA. However, blockade of D2 dopamine receptors (D2R) significantly attenuated LTDGABA proposing a novel synaptic mechanism for the regulation of excitability of DA neurons by endogenous DA and D2R activation. Interestingly, 24 h after a single in vivo exposure to morphine, LTDGABA 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. This article is part of a Special Issue entitled ‘Synaptic Plasticity and Addiction’. [Copyright &y& Elsevier]

Abstract: 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 drug-induced 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. This article is part of a Special Issue entitled ‘Synaptic Plasticity and Addiction’. [Copyright &y& Elsevier]

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. Methodology/Principal Findings: If hungry bees are fed with sucrose, they will release a long lasting PER; however, this PER can be interrupted if an odor is presented 15 seconds (but not 7 or 30 seconds) after the sucrose (backward pairing). We refer to this previously unreported process as olfactory interference. Bees receiving this 15 second backward pairing show reduced performance after a subsequent single forward pairing (excitatory conditioning) trial. Analysis of the results supported a relationship between olfactory interference and a form of backward pairing-induced inhibitory learning/memory. Injecting the drug cimetidine into the deutocerebrum impaired olfactory interference. Conclusions/Significance: Olfactory interference depends on the associative link between odor and PER, rather than between odor and sucrose. Furthermore, pairing an odor with sucrose can lead either to association of this odor to PER or to the inhibition of PER by this odor. Olfactory interference may provide insight into processes that gate how excitatory and inhibitory memories for odor-PER associations are formed. [ABSTRACT FROM AUTHOR]

Abstract: In the honeybee Apis mellifera, multiple-trial olfactory conditioning of the proboscis extension response specifically leads to long-term memory (LTM) which can be retrieved more than 24h after learning. We studied the involvement of nicotinic acetylcholine receptors in the establishment of LTM by injecting the nicotinic antagonists mecamylamine (1mM), α-bungarotoxin (α-BGT, 0.1mM) or methyllycaconitine (MLA, 0.1mM) into the brain through the median ocellus 20min before or 20min after multiple-trial learning. The retention tests were performed 1, 3, and 24h after learning. Pre-training injections of mecamylamine induced a lower performance during conditioning but had no effect on LTM formation. Post-training injections of mecamylamine did not affect honeybees’ performances. Pre-training injections of MLA or post-training injection of α-BGT specifically induced LTM impairment whereas acquisition as well as memory retrieval tested 1 or 3h after learning was normal. This indicates that brain injections of α-BGT and MLA did not interfere with learning or medium-term memory. Rather, these blockers affect the LTM. To explain these results, we advance the hypothesis that honeybee α-BGT-sensitive acetylcholine receptors are also sensitive to MLA. These receptors could be essential for triggering intracellular mechanisms involved in LTM. By contrast, medium-term memory is not dependent upon these receptors but is affected by mecamylamine. [Copyright &y& Elsevier]

Abstract: Fipronil is a phenylpyrazole insecticide introduced for pest control, but it can also affect non-target insects such as honeybees. In insects, fipronil is known to block GABA receptors and to inhibit ionotropic glutamate-gated chloride channels, but the behavioral effects of low doses are not yet fully understood. We have studied the effect of sublethal doses of fipronil on the behavior of the honeybee (Apis mellifera) under controlled laboratory conditions. The drug was either administered orally or applied topically on the thorax. A significant reduction of sucrose sensitivity was observed for the dose of 1 ng/bee 1 h after a thoracic application. No significant effect on sucrose sensitivity was obtained with acute oral treatment. A lower dose of fipronil (0.5 ng/bee applied topically) impaired the olfactory learning of the honeybees. By contrast, locomotor activity was not affected. Our results suggest a particular vulnerability of the olfactory memory processes and sucrose perception to sublethal doses of fipronil in the honeybee. [Copyright &y& Elsevier]

Provides information on a study that analyzed regional brain variations of cytochrome oxidase staining in the honeybee after olfactory conditioning of the proboscis extension reflex. Methodology of the study; Results and discussion on the study.

In many animals, drastic changes are observed during sexual maturation characterized by the reproductive system development concomitantly to the sexual behavior ontogenesis. These modifications are under the control of internal and external factors such as food. Sexual maturation requires considerable energetic investment, and diet has been shown to affect reproductive activities in many taxonomic groups, especially in insects and vertebrates. By contrast, diet effects on sexual behavior development remain largely unexplored. To elucidate this aspect, we used the male moth Agrotis ipsilon which undergoes sexual maturation occurring between the third and the fifth day postemergence. During this period, males are sensitive to female sex pheromones and a stereotypical sexual behavior characterized by female‐oriented flight takes place. In our study, we compared (1) sex pheromone detection by electroantennography recordings and (2) behavioral response in wind tunnel assays between males fed with different diets found in nature. Compared to standard sucrose diet, males fed with sucrose, fructose, and glucose supplemented with sodium (a mineral element necessary for the locomotor activity in several moths) did not respond better to female sex pheromones but clearly exhibited an earlier behavioral response. Thus, such a diet accelerates the development of sex pheromone‐mediated oriented flight, probably by facilitating the central processing of sex pheromone information in male A. ipsilon moths. Our results provide new information on the influence of nutritional intake on the ontogenesis of male sexual behavior in animals. [ABSTRACT FROM AUTHOR]

• The BeeBox automatically records feeding time and occurrence in insects. • This reveals circadian rhythm in feeding in bees. • This rhythm is lost in animals kept in constant light. • Constant light also induces higher mortality. In honey bees, most studies of circadian rhythms involve a locomotion test performed in a small tube, a tunnel, or at the hive entrance. However, despite feeding playing an important role in honey bee health or fitness, no demonstration of circadian rhythm on feeding has been performed until recently. Here, we present the BeeBox, a new laboratory platform for bees based on the concept of the Skinner box, which dispenses discrete controlled amounts of food (sucrose syrup) following entrance into an artificial flower. We compared caged groups of bees in 12 h-12 h light/dark cycles, constant darkness and constant light and measured average hourly syrup consumption per living bee. Food intake was higher in constant light and lower in constant darkness; mortality increased in constant light. We observed rhythmic consumption with a period longer than 24 h; this is maintained in darkness without environmental cues, but is damped in the constant light condition. The BeeBox offers many new research perspectives and numerous potential applications in the study of nectar foraging animals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diet is linked to reproductive system maturation in adult male Agrotis ipsilon. • Development of accessory sex glands is promoted by diet rich in sugars and sodium. • Diversified sugars and sodium accelerate testicular development and sperm transfer. In male moth Agrotis ipsilon , sexual maturation occurs between the third and the fifth day of adult life and is characterized by the development of the reproductive organs such as testes and accessory sex glands. Since sexual maturation requires considerable energy investment, we hypothesized that diet would be an essential regulatory factor in this developmental process. Indeed, the links between the male diet and reproductive physiology have not been described as in females. To test the previous hypothesis, we offered male moths diets corresponding to different flower nectars found in nature, and measured morphological and functional changes in the testes and accessory sex glands. In comparison to a diet composed of sucrose only, males fed with a diet composed of diverse sugars, including glucose, supplemented with sodium led to an earlier increase in the length and the protein content of accessory sex glands, as well as a reduction of the testicular volume accompanied by an acceleration of the sperm bundle transfer from the testes to the duplex. These results show that these specific diets accelerate the maturation of the reproductive system in male moth Agrotis ipsilon. [ABSTRACT FROM AUTHOR]

During leaf senescence, nitrogen is remobilized and carbon backbones are replenished by amino acid catabolism, with many of the key reactions occurring in mitochondria. The intermediate Δ1‐pyrroline‐5‐carboxylate (P5C) is common to some catabolic pathways, thus linking the metabolism of several amino acids, including proline and arginine. Specifically, mitochondrial proline catabolism involves sequential action of proline dehydrogenase (ProDH) and P5C dehydrogenase (P5CDH) to produce P5C and then glutamate. Arginine catabolism produces urea and ornithine, the latter in the presence of α‐ketoglutarate being converted by ornithine δ‐aminotransferase (OAT) into P5C and glutamate. Metabolic changes during dark‐induced leaf senescence (DIS) were studied in Arabidopsis thaliana leaves of Col‐0 and in prodh1prodh2, p5cdh and oat mutants. Progression of DIS was followed by measuring chlorophyll and proline contents for 5 days. Metabolomic profiling of 116 compounds revealed similar profiles of Col‐0 and oat metabolism, distinct from prodh1prodh2 and p5cdh metabolism. Metabolic dynamics were accelerated in p5cdh by 1 day. Notably, more P5C and proline accumulated in p5cdh than in prodh1prodh2. ProDH1 enzymatic activity and protein amount were significantly down‐regulated in p5cdh mutant at Day 4 of DIS. Mitochondrial P5C levels appeared critical in determining the flow through interconnected amino acid remobilization pathways to sustain senescence. Summary statement: Metabolic profiling revealed a key role of proline dehydrogenase (ProDH) and pyrroline‐5‐carboxylate dehydrogenase (P5CDH) but not of ornithine aminotransferase in proline oxidation during Arabidopsis dark‐induced leaf senescence (DIS). P5CDH‐dependent regulation of ProDH appears to be necessary to partition the limited resources during DIS to ensure the Krebs cycle to be fuelled with TCA intermediates for remobilization of the remaining nitrogen in the leaf. [ABSTRACT FROM AUTHOR]

Mate finding in most moths is based on male perception of a female-emitted pheromone whose species specificity resides in component chemistry and proportions. Components are individually detected by specialized olfactory receptor neurons (ORNs) projecting into the macroglomerular complex (MGC) of the male brain. We asked how robust ratio recognition is when challenged by a plant volatile background. To test this, we investigated the perception of the pheromone blend in Agrotis ipsilon, a moth species whose females produce a blend of Z7-dodecenyl acetate (Z7-12:Ac), Z9-tetradecenyl acetate (Z9-14:Ac), and Z11-hexadecenyl acetate in a 4:1:4 ratio optimally attractive for males. First, we recorded the responses of specialist ORNs for Z7 and Z9 and showed that heptanal, a flower volatile, activated Z7 but not Z9 neurons. Then, we recorded intracellularly the responses of MGC neurons to various ratios and showed that heptanal altered ratio responses of pheromone-sensitive neurons. Finally, we analyzed the behavior of males in a wind tunnel and showed that their innate preference for the 4:1:4 blend was shifted in the presence of heptanal. Pheromone ratio recognition may thus be altered by background odorants. Therefore, the olfactory environment might be a selective force for the evolution of pheromone communication systems. [ABSTRACT FROM AUTHOR]

Endocrine-disrupting chemicals encompass a variety of chemicals that may interfere with the endocrine system and produce negative effects on organisms. Among them, bisphenol A is considered a major pollutant in numerous countries. The harmful effects of BPA on environmental and human health are intensely studied. However, the effects of BPA on terrestrial insects are still poorly investigated, despite that several plants can accumulate BPA in their tissues, leading to potential contamination of herbivorous insects. Here, we used the leafworm Spodoptera littoralis, a polyphagous species, to study BPA effects on post-embryonic development. We studied the effects of BPA ingestion at environmental doses (e.g., 0.01, 0.1, and 1 μg/g of BPA) and high doses (e.g., 25 μg/g) on larval weight and stage duration, pupal length and sex ratio. BPA effects were investigated in more detail during the last larval instar, a crucial period for preparing pupation and metamorphosis, which are under endocrine control. We monitored the haemolymph concentration of ecdysteroids, hormones controlling moult and metamorphosis, as well as the expression levels of several nuclear receptors involved in the ecdysteroid signalling pathway. Our integrative study showed that, upon exposure doses, BPA can induce various effects on the viability, developmental time, growth and sex ratio. These effects were correlated with a delay of the ecdysteroid peak during the last larval instar and a modification of expression of EcR, USP, E75AB, E75D and Br-c. We provide new evidence about the events that occur after BPA exposure in insect contaminated by food ingestion. • Ingestion of BPA induced effects on mortality, development and growth. • Ingestion of BPA disrupted the ecdysteroid peak in last larval stage. • BPA disrupted the expression of nuclear receptor in last larval stage. [ABSTRACT FROM AUTHOR]

Abstract 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 post-embryonic 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. Highlights • DEHP was present in all stages, with higher concentrations in chrysalises and adults than in larvae. • Only the two highest DEHP doses induced higher insect mortality, whereas low and intermediate concentrations increased larval food consumption without affecting body weight. • DEHP alter hemolymphatic ecdysteroid titers and expression levels of ecdysteroid response genes. • DEHP can alter insect post-embryonic development by interfering with ecdysteroid pathways. [ABSTRACT FROM AUTHOR]

Dopamine (DA) dysfunction originating from the ventral tegmental area (VTA) occurs as a result of synaptic abnormalities following consumption of drugs of abuse and underlies behavioral plasticity associated with drug abuse. Drugs of abuse can cause changes in gene expression through epigenetic mechanisms in the brain that underlie some of the lasting neuroplasticity and behavior associated with addiction. Here we investigated the function of histone acetylation and histone deacetylase (HDAC)2 in the VTA in recovery of morphine-induced synaptic modifications following a single in vivo exposure to morphine. Using a combination of immunohistochemistry, Western blot, and whole cell patch-clamp recording in rat midbrain slices, we show that morphine increased HDAC2 activity in VTA DA neurons and reduced histone H3 acetylation at lysine 9 (Ac-H3K9) in the VTA 24 h after the injection. Morphine-induced synaptic changes at glutamatergic synapses involved endocannabinoid signaling to reduce GABAergic synaptic strength onto VTA DA neurons. Both plasticities were recovered by in vitro incubation of midbrain slices with a class I-specific HDAC inhibitor (HDACi), CI-994, through an increase in acetylation of histone H3K9. Interestingly, HDACi incubation also increased levels of Ac-H3K9 and triggered GABAergic and glutamatergic plasticities in DA neurons of saline-treated rats. Our results suggest that acute morphine-induced changes in VTA DA activity and synaptic transmission engage HDAC2 activity locally in the VTA to maintain synaptic modifications through histone hypoacetylation. [ABSTRACT FROM AUTHOR]

The behavioural lateralization observed in several invertebrate species appears to parallel the phenomenon seen in vertebrates. However, it is not yet clear whether lateralization in invertebrates varies within an individual across development as it does in vertebrates. We examined when during postembryonic development juvenile cuttlefish begin to show side-turning preferences in a T-shaped apparatus. We also determined whether or not the direction of turning was stimulus dependent by providing, or not providing, shelters in the two choice arms of the apparatus. We found that as the animals aged from 3 to 45days posthatch they progressively developed a left-turning bias but only when shelters were provided in the apparatus. We suggest that left-turning biases in cuttlefish result from an eye use preference. Emergence of visual lateralization at the time of dispersal may afford juveniles greater behavioural efficiency by enabling them to look out for escape routes while hunting. The left visual field may be associated with rapid responses as in many species of vertebrates. Determining the role of the right visual field of cuttlefish when looking for prey may provide evidence for homology between lateralization in invertebrates and vertebrates. [Copyright &y& Elsevier]

Abstract: Environmental enrichment is known to improve learning and memory in adult rodents. Whereas the morphological changes underlying these beneficial effects are well documented, few studies have addressed the influence of this housing condition on the neuronal networks underlying memory processes. We assessed the effects of environmental enrichment on behavioural performances and brain metabolic activation during a memory task in mice. Adult mice were housed in standard (SC) or enriched (EC) conditions for 3 weeks. Then, recent and remote memory performances were measured in the passive avoidance test. After testing, brain metabolic activation was assessed through cytochrome oxidase (CO) activity. EC improved recent memory, in association with an increased metabolic activation in the frontal and prefrontal cortices and a decreased activation in the baso-lateral amygdala and the hippocampus. EC did not improve remote memory, and globally decreased CO activity. Our findings suggest the involvement of regions of pivotal importance during recent memory, such as the frontal cortex, in the beneficial effects of EC. [Copyright &y& Elsevier]

Pheromones are chemical communication signals known to elicit stereotyped behaviours and/or physiological processes in individuals of the same species, generally in relation to a specific function (e.g. mate finding in moths). However, recent research suggests that pheromones can modulate behaviours, which are not directly related to their usual function and thus potentially affect behavioural plasticity. To test this hypothesis, we studied the possible modulatory effects of pheromones on olfactory learning and memory in Agrotis ipsilon moths, which are well-established models to study sex-pheromones. To achieve this, sexually mature male moths were trained to associate an odour with either a reward (appetitive learning) or punishment (aversive learning) and olfactory memory was tested at medium- and long-term (1 h or 1.5 h, and 24 h). Our results show that male moths can learn to associate an odour with a sucrose reward, as well as a mild electric shock, and that olfactory memory persists over medium- and long-term range. Pheromones facilitated both appetitive and aversive olfactory learning: exposure to the conspecific sex-pheromone before conditioning enhanced appetitive but not aversive learning, while exposure to a sex-pheromone component of a heterospecific species (repellent) facilitated aversive but not appetitive learning. However, this effect was short-term, as medium- and long-term memory were not improved. Thus, in moths, pheromones can modulate olfactory learning and memory, indicating that they contribute to behavioural plasticity allowing optimization of the animal's behaviour under natural conditions. This might occur through an alteration of sensitization. [ABSTRACT FROM AUTHOR]

Bis(2-ethylhexyl) phthalate (DEHP) is a widely produced plasticizer that is considered to act as an endocrine-disrupting chemical in vertebrates and invertebrates. Indeed, many studies have shown that DEHP alters hormonal levels, reproduction and behavior in vertebrates. Few studies have focused on the effects of DEHP on insects, although DEHP is found almost everywhere in their natural habitats, particularly in soils and plants. Here, we investigated the effects of DEHP on the sexual behavior and physiology of a pest insect, the noctuid moth Spodoptera littoralis. In this nocturnal species, olfaction is crucial for sexual behavior, and ecdysteroids at the antennal level have been shown to modulate sex pheromone detection by males. In the present study, larvae were fed food containing different DEHP concentrations, and DEHP concentrations were then measured in the adults (males and females). Hemolymphatic ecdysteroid concentrations, the antennal expression of genes involved in the ecdysteroid pathway (nuclear receptors EcR , USP , E75 , and E78 and calmodulin) and sexual behavior were then investigated in adult males. The success and latency of mating as well as the hatching success were also studied in pairs consisting of one DEHP male and one uncontaminated female or one DEHP female and one uncontaminated male. We also studied the offspring produced from pairs involving contaminated females to test the transgenerational effect of DEHP. Our results showed the general downregulation of nuclear receptors and calmodulin gene expression associated with the higher concentrations of DEHP, suggesting peripheral olfactory disruption. We found some effects on male behavior but without an alteration of the mating rate. Effects on offspring mortality and developmental rates in the N + 1 generation were also found at the higher doses of DEHP. Taken together, the results of the study show for the first time that larval exposure to DEHP can induce delayed endocrine-disruptive effects in the adults of a terrestrial insect as well as effects on the next generation. To date, our study is also the first description of an impact of endocrine disrupter on olfaction in insects. • Larval exposure to DEHP induced delayed effects on adults and the next generation. • The expression of ecdysteroid responsive genes in male antennae was reduced. • DEHP altered some male sexual behavior's items, but not the mating rate. • The observed effects on mating duration and hatching success were sex-dependent. • The duration of larval stages and adult lifespan of offspring were altered. [ABSTRACT FROM AUTHOR]