Nicotinic acetylcholine receptor (nAChR) mediated dopamine release in larval Drosophila melanogaster

Modulation of dopamine, serotonin, and behavior by lutein carrier nanoparticles in a Drosophila melanogaster model of neurodevelopmental disorders

Considering that woman's health during pregnancy is crucial to well-being as much maternal and fetal as well as the child's future, supplementation with antioxidant compounds has emerged as a promising strategy to prevent the development of future diseases. Given this context, the study aimed to evaluate the effect of lutein carrier nanoparticles supplementation during the preconception period on the offspring of Drosophila melanogaster subjected to a neurodevelopmental disorder model. Female flies, were exposed to either a standard diet or a diet containing NPs LUT (6 μM) for 24 h. Following this period, the flies were transferred to new experimental vials, and eighteen males were added, resulting in a total of 53 flies per experimental group. The male and female flies were then subdivided into two groups and exposed to either a standard diet or imidacloprid (IMI), for 7 days, to induce the neurodevelopmental disorder model, creating four experimental groups: 1) Control; 2) IMI; 3) NPs LUT; 4) NPs LUT + IMI. The hatched offspring were then used for behavioral and biochemical evaluations. Our results showed that supplementation with lutein carrier nanoparticles was able to prevent decreased activity of enzyme tyrosine hydroxylase (TH), as did neurotransmitters dopamine (DA) and serotonin (5-HT) in the head of flies, and as a consequence it prevented behavioral damages such as hyperactivity, anxiety, social interaction, repetitive movements, learning and memory in the progeny of both sexes. Thus, these findings highlight the relevance of preconception supplementation with lutein carrier nanoparticles as an effective approach to prevent the emergence of symptoms associated with neuropsychiatric disorders, paving the way for future research aimed at investigating the best intervention period to prevent ASD and ADHD-type disorders.

Thiamethoxam at environmentally relevant concentrations induces neurotoxicity in zebrafish larvae through binding with multiple receptors

Thiamethoxam (THM) is one of the most widely used insecticides globally, which was designed to selectively target nicotinic acetylcholine receptors (nAChRs) in the insect nervous system and is generally considered safe for non-targeted organisms. However, increasing evidence has demonstrated its neurotoxicity in aquatic organisms, though the underlying mechanisms, especially at environmentally relevant concentrations, remain largely unclear. In this study, the swimming distance of zebrafish was significantly shortened by 14.06%-21.64% after exposure to THM at 10-1000 ng/L. This behavioral impairment may result from the damage to nervous and visual systems, as confirmed by notable apoptosis, histological analysis of the eyes, and differential expression of numerous genes. Molecular docking and biomarkers assays found that THM can bind with nAChR and multiple hormone receptors, with binding energies varying from -3.75 to -6.74 kcal/mol. Consequently, the concentrations of a neurotransmitter (acetylcholine) and related hormones (cortisol, triiodothyronine, thyroxine, and thyroid-stimulating hormone) were significantly affected. Further investigations using a weighted gene correlation network and metabolomics suggest that THM may enter the cell via endocytosis and bind with multiple hormone receptors, potentially activating the MAPK signaling pathway. This activation may disrupt purine and pyrimidine metabolism in the cell nucleus, ultimately leading to cell apoptosis and neurotoxicity. This study reveals that THM, even at environmentally relevant concentrations, poses neurological risks to zebrafish and underscore the need for urgent attention to the ecological impacts of THM in aquatic environments.

A drug repurposing screen reveals dopamine signaling as a critical pathway underlying potential therapeutics for the rare disease DPAGT1-CDG

DPAGT1-CDG is a Congenital Disorder of Glycosylation (CDG) that lacks effective therapies. It is caused by mutations in the gene DPAGT1 which encodes the first enzyme in N-linked glycosylation. We used a Drosophila rough eye model of DPAGT1-CDG with an improperly developed, small eye phenotype. We performed a drug repurposing screen on this model using 1,520 small molecules that are 98% FDA/EMA-approved to find drugs that improved its eye. We identified 42 candidate drugs that improved the DPAGT1-CDG model. Notably from this screen, we found that pharmacological and genetic inhibition of the dopamine D2 receptor partially rescued the DPAGT1-CDG model. Loss of both dopamine synthesis and recycling partially rescued the model, suggesting that dopaminergic flux and subsequent binding to D2 receptors is detrimental under DPAGT1 deficiency. This links dopamine signaling to N-glycosylation and represents a new potential therapeutic target for treating DPAGT1-CDG. We also genetically validate other top drug categories including acetylcholine-related drugs, COX inhibitors, and an inhibitor of NKCC1. These drugs and subsequent analyses reveal novel biology in DPAGT1 mechanisms, and they may represent new therapeutic options for DPAGT1-CDG.

Comparative analysis of tardigrade locomotion across life stage, species, and disulfiram treatment

Animal locomotion requires coordination between the central and peripheral nervous systems, between sensory inputs and motor outputs, and between nerves and muscles. Analysis of locomotion thus provides a comprehensive and sensitive readout of nervous system function and dysfunction. Tardigrades, the smallest known walking animals, coordinate movement of their eight legs with a relatively simple nervous system, and are a promising model for neuronal control of limb-driven locomotion. Here, we developed open-source tools for automated tracking of tardigrade locomotion in an unconstrained two-dimensional environment, for measuring multiple parameters of individual leg movements, and for quantifying interleg coordination. We used these tools to analyze >13,000 complete strides in >100 tardigrades, and identified preferred walking speeds and distinct step coordination patterns associated with those speeds. In addition, the rear legs of tardigrades, although they have distinct anatomy and step kinematics, were nonetheless incorporated into overall patterns of interleg coordination. Finally, comparisons of tardigrade locomotion across lifespan, between species, and upon disulfiram treatment suggested that neuronal regulation of high-level aspects of walking (e.g. speed, turns, walking bout initiation) operate independently from circuits controlling individual leg movements and interleg coordination.

Aquatic ecological risk assessment of imidacloprid and thiacloprid in an urban river of Qingdao, China

Imidacloprid and thiacloprid, two neonicotinoid insecticides that are extensively used in urban areas, are potentially toxic to non-target aquatic organisms. In this study, the concentrations of imidacloprid and thiacloprid in surface runoff after rainfall were 20.79-43.77 ng/L and 25.13-63.84 ng/L, respectively, whereas the levels for the Licun River were 10.78-41.70 ng/L and 2.66-39.68 ng/L, respectively. The acute and chronic criteria for imidacloprid and thiacloprid are 0.865, 0.006, 0.83, and 0.012 μg/L, respectively. Tiered ecological risk assessments revealed the chronic ecological risks of these micropollutants to local aquatic species. There was a moderate chronic toxicity risk associated with imidacloprid and thiacloprid in the Licun River, and the joint probability curves showed a probability of chronic ecological risk to 5 % of the aquatic organisms at 68 %-97 %. The results provide evidence of urban surface runoff transporting micropollutants from surface into rivers and estuaries, highlighting the ecological risks to aquatic ecosystems.

Associative gene networks reveal novel candidates important for ADHD and dyslexia comorbidity

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is commonly associated with developmental dyslexia (DD), which are both prevalent and complicated pediatric neurodevelopmental disorders that have a significant influence on children's learning and development. Clinically, the comorbidity incidence of DD and ADHD is between 25 and 48%. Children with DD and ADHD may have more severe cognitive deficiencies, a poorer level of schooling, and a higher risk of social and emotional management disorders. Furthermore, patients with this comorbidity are frequently treated for a single condition in clinical settings, and the therapeutic outcome is poor. The development of effective treatment approaches against these diseases is complicated by their comorbidity features. This is often a major problem in diagnosis and treatment. In this study, we developed bioinformatical methodology for the analysis of the comorbidity of these two diseases. As such, the search for candidate genes related to the comorbid conditions of ADHD and DD can help in elucidating the molecular mechanisms underlying the comorbid condition, and can also be useful for genotyping and identifying new drug targets.

RESULTS

Using the ANDSystem tool, the reconstruction and analysis of gene networks associated with ADHD and dyslexia was carried out. The gene network of ADHD included 599 genes/proteins and 148,978 interactions, while that of dyslexia included 167 genes/proteins and 27,083 interactions. When the ANDSystem and GeneCards data were combined, a total of 213 genes/proteins for ADHD and dyslexia were found. An approach for ranking genes implicated in the comorbid condition of the two diseases was proposed. The approach is based on ten criteria for ranking genes by their importance, including relevance scores of association between disease and genes, standard methods of gene prioritization, as well as original criteria that take into account the characteristics of an associative gene network and the presence of known polymorphisms in the analyzed genes. Among the top 20 genes with the highest priority DRD2, DRD4, CNTNAP2 and GRIN2B are mentioned in the literature as directly linked with the comorbidity of ADHD and dyslexia. According to the proposed approach, the genes OPRM1, CHRNA4 and SNCA had the highest priority in the development of comorbidity of these two diseases. Additionally, it was revealed that the most relevant genes are involved in biological processes related to signal transduction, positive regulation of transcription from RNA polymerase II promoters, chemical synaptic transmission, response to drugs, ion transmembrane transport, nervous system development, cell adhesion, and neuron migration.

CONCLUSIONS

The application of methods of reconstruction and analysis of gene networks is a powerful tool for studying the molecular mechanisms of comorbid conditions. The method put forth to rank genes by their importance for the comorbid condition of ADHD and dyslexia was employed to predict genes that play key roles in the development of the comorbid condition. The results can be utilized to plan experiments for the identification of novel candidate genes and search for novel pharmacological targets.

Expression of subunits of an insecticide target receptor varies across tissues, life stages, castes, and species of social bees

Global losses of insects jeopardize ecosystem stability and crop pollination. Robust evidence indicates that insecticides have contributed to these losses. Notably, insecticides targeting nicotinic acetylcholine receptors (nAChRs) have neurotoxic effects on beneficial insects. Because each nAChR consists of five subunits, the alternative arrangements of subunits could create a multitude of receptors differing in structure and function. Therefore, understanding whether the use of subunits varies is essential for evaluating and predicting the effects of insecticides targeting such receptors. To better understand how the use and composition of nAChRs differ within and between insect pollinators, we analysed RNA-seq gene expression data from tissues and castes of Apis mellifera honey bees and life stages and castes of the Bombus terrestris bumble bees. We reveal that all analysed tissues express nAChRs and that relative expression levels of nAChR subunits vary widely across almost all comparisons. Our work thus shows fine-tuned spatial and temporal expression of nAChRs. Given that coexpression of subunits underpins the compositional diversity of functional receptors and that the affinities of insecticides depend on nAChR composition, our findings provide a likely mechanism for the various damaging effects of nAChR-targeting insecticides on insects. Furthermore, our results indicate that the appraisal of insecticide risks should carefully consider variation in molecular targets.

Fast-Scan Cyclic Voltammetry (FSCV) Reveals Behaviorally Evoked Dopamine Release by Sugar Feeding in the Adult Drosophila Mushroom Body

Drosophila melanogaster, the fruit fly, is an excellent model organism for studying dopaminergic mechanisms and simple behaviors, but methods to measure dopamine during behavior are needed. Here, we developed fast-scan cyclic voltammetry (FSCV) to track in vivo dopamine during sugar feeding. First, we employed acetylcholine stimulation to evaluate the feasibility of in vivo measurements in an awake fly. Next, we tested sugar feeding by placing sucrose solution near the fly proboscis. In the mushroom body medial tip, 1 pmol acetylcholine and sugar feeding released 0.49±0.04 μM and 0.31±0.06 μM dopamine, respectively but sugar-evoked release lasted longer than with acetylcholine. Administering the dopamine transporter inhibitor nisoxetine or D2 receptor antagonist flupentixol significantly increased sugar-evoked dopamine. This study develops FSCV to measure behaviorally evoked release in fly, enabling Drosophila studies of neurochemical control of reward, learning, and memory behaviors.

SSRI antidepressants differentially modulate serotonin reuptake and release in Drosophila

Selective serotonin reuptake inhibitor (SSRI) antidepressants are commonly prescribed treatments for depression, but their effects on serotonin reuptake and release are not well understood. Drosophila melanogaster, the fruit fly, expresses the serotonin transporter (dSERT), the major target of SSRIs, but real-time serotonin changes after SSRIs have not been characterized in this model. The goal of this study was to characterize effects of SSRIs on serotonin concentration and reuptake in Drosophila larvae. We applied various doses (0.1-100 μM) of fluoxetine (Prozac), escitalopram (Lexapro), citalopram (Celexa), and paroxetine (Paxil), to ventral nerve cord (VNC) tissue and measured optogenetically-stimulated serotonin release with fast-scan cyclic voltammetry (FSCV). Fluoxetine increased reuptake from 1 to 100 μM, but serotonin concentration only increased at 100 μM. Thus, fluoxetine occupies dSERT and slows clearance but does not affect concentration. Escitalopram and paroxetine increased serotonin concentrations at all doses, but escitalopram increased reuptake more. Citalopram showed lower concentration changes and faster reuptake profiles compared with escitalopram, so the racemic mixture of citalopram does not change reuptake as much as the S-isomer. Dose response curves were constructed to compare dSERT affinities and paroxetine showed the highest affinity and fluoxetine the lowest. These data demonstrate SSRI mechanisms are complex, with separate effects on reuptake or release. Furthermore, dynamic serotonin changes in Drosophila are similar to previous studies in mammals. This work establishes how antidepressants affect serotonin in real-time, which is useful for future studies that will investigate pharmacological effects of SSRIs with different genetic mutations in Drosophila.

Constructing and Tuning Excitatory Cholinergic Synapses: The Multifaceted Functions of Nicotinic Acetylcholine Receptors in Drosophila Neural Development and Physiology

Nicotinic acetylcholine receptors (nAchRs) are widely distributed within the nervous system across most animal species. Besides their well-established roles in mammalian neuromuscular junctions, studies using invertebrate models have also proven fruitful in revealing the function of nAchRs in the central nervous system. During the earlier years, both in vitro and animal studies had helped clarify the basic molecular features of the members of the Drosophila nAchR gene family and illustrated their utility as targets for insecticides. Later, increasingly sophisticated techniques have illuminated how nAchRs mediate excitatory neurotransmission in the Drosophila brain and play an integral part in neural development and synaptic plasticity, as well as cognitive processes such as learning and memory. This review is intended to provide an updated survey of Drosophila nAchR subunits, focusing on their molecular diversity and unique contributions to physiology and plasticity of the fly neural circuitry. We will also highlight promising new avenues for nAchR research that will likely contribute to better understanding of central cholinergic neurotransmission in both Drosophila and other organisms.

Associative learning in larval and adult Drosophila is impaired by the dopamine-synthesis inhibitor 3-Iodo-L-tyrosine

Across the animal kingdom, dopamine plays a crucial role in conferring reinforcement signals that teach animals about the causal structure of the world. In the fruit fly Drosophila melanogaster, dopaminergic reinforcement has largely been studied using genetics, whereas pharmacological approaches have received less attention. Here, we apply the dopamine-synthesis inhibitor 3-Iodo-L-tyrosine (3IY), which causes acute systemic inhibition of dopamine signaling, and investigate its effects on Pavlovian conditioning. We find that 3IY feeding impairs sugar-reward learning in larvae while leaving task-relevant behavioral faculties intact, and that additional feeding of a precursor of dopamine (L-3,4-dihydroxyphenylalanine, L-DOPA), rescues this impairment. Concerning a different developmental stage and for the aversive valence domain. Moreover, we demonstrate that punishment learning by activating the dopaminergic neuron PPL1-γ1pedc in adult flies is also impaired by 3IY feeding, and can likewise be rescued by L-DOPA. Our findings exemplify the advantages of using a pharmacological approach in combination with the genetic techniques available in D. melanogaster to manipulate neuronal and behavioral function.

Summary: We surveyed the effects of a dopamine-synthesis inhibitor on associative learning in larval and adult Drosophila. This approach can supplement genetic tools in investigating the conserved reinforcing function of dopamine.

Oxidative stress and decreased dopamine levels induced by imidacloprid exposure cause behavioral changes in a neurodevelopmental disorder model in Drosophila melanogaster

Neurodevelopmental disorders, such as Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) are responsible for behavioral deficits in children. Imidacloprid is a nicotinic acetylcholine receptor agonist, capable of causing behavioral changes in Drosophila melanogaster, similar to the ADHD-like phenotypes. We assess whether behavioral damage induced by imidacloprid exposure in Drosophila melanogaster is associated with neurochemical changes and whether these changes are similar to those observed in neurodevelopmental disorders such as ASD and ADHD. The fruit flies were divided into four groups, exposed to either a standard diet (control) or a diet containing imidacloprid (200, 400 or 600 ρM) and allowed to mate for 7 days. After hatching, the progeny was subjected to in vivo and ex vivo tests. The ones exposed to imidacloprid showed an increase in hyperactivity, aggressiveness, anxiety and repetitive movements, as well as, a decrease in social interaction. Furthermore, exposure to imidacloprid decreased dopamine levels, cell viability and increased oxidative stress in the flies' progeny. These results demonstrated that the behavioral damage induced by imidacloprid exposure involves a reduction in dopamine levels and oxidative stress and that these neurochemical changes are in line with the events that occur in ASD and ADHD-like phenotypes in other models.

Ring Finger Protein 11 (RNF11) Modulates Dopamine Release in Drosophila

Recent work indicates a role for RING finger protein 11 (RNF11) in Parkinson disease (PD) pathology, which involves the loss of dopaminergic neurons. However, the role of RNF11 in regulating dopamine neurotransmission has not been studied. In this work, we tested the effect of RNF11 RNAi knockdown or overexpression on stimulated dopamine release in the larval Drosophila central nervous system. Dopamine release was stimulated using optogenetics and monitored in real-time using fast-scan cyclic voltammetry at an electrode implanted in an isolated ventral nerve cord. RNF11 knockdown doubled dopamine release, but there was no decrease in dopamine from RNF11 overexpression. RNF11 knockdown did not significantly increase stimulated serotonin or octopamine release, indicating the effect is dopamine specific. Dopamine clearance was also changed, as RNF11 RNAi flies had a higher V_max and RNF11 overexpressing flies had a lower V_max than control flies. RNF11 RNAi flies had increased mRNA levels of dopamine transporter (DAT) in RNF11, confirming changes in DAT. In RNF11 RNAi flies, release was maintained better for stimulations repeated at short intervals, indicating increases in the recycled releasable pool of dopamine. Nisoxetine, a DAT inhibitor, and flupenthixol, a D2 antagonist, did not affect RNF11 RNAi or overexpressing flies differently than control. Thus, RNF11 knockdown causes early changes in dopamine neurotransmission, and this is the first work to demonstrate that RNF11 affects both dopamine release and uptake. RNF11 expression decreases in human dopaminergic neurons during PD, and that decrease may be protective by increasing dopamine neurotransmission in the surviving dopaminergic neurons.

Real-Time Measurement of Stimulated Dopamine Release in Compartments of the Adult Drosophila melanogaster Mushroom Body

Drosophila melanogaster, a fruit fly, is an exquisite model organism to understand neurotransmission. Dopaminergic signaling in the Drosophila mushroom body (MB) is involved in olfactory learning and memory, with different compartments controlling aversive learning (heel) vs. appetitive learning (medial tip). Here, the goal was to develop techniques to measure endogenous dopamine in compartments of the MB for the first time. We compared three stimulation methods: acetylcholine (natural stimulus), P2X₂ (chemogenetics), and CsChrimson (optogenetics). Evoked dopamine release was measured with fast-scan cyclic voltammetry in isolated adult Drosophila brains. Acetylcholine stimulated the largest dopamine release (0.40 μM) followed by P2X₂ (0.14 μM) and CsChrimson (0.07 μM). With the larger acetylcholine and P2X₂ stimulations, there were no regional or sex differences in dopamine release. However, with CsChrimson, dopamine release was significantly higher in the heel than the medial tip, and females had more dopamine than males. Michaelis-Menten modeling of the single-light pulse revealed no significant regional differences in K_m, but the heel had a significantly lower V_max (0.12 μM/s vs. 0.19 μM/s) and higher dopamine release (0.05 μM vs. 0.03 μM). Optogenetic experiments are challenging because CsChrimson is also sensitive to blue light used to activate green fluorescent protein, and thus, light exposure during brain dissection must be minimized. These experiments expand the toolkit for measuring endogenous dopamine release in Drosophila, introducing chemogenetic and optogenetic experiments for the first time. With a variety of stimulations, different experiments will help improve our understanding of neurochemical signaling in Drosophila.

Neuroprotective Effect of Curcumin on the Nigrostriatal Pathway in a 6-Hydroxydopmine-Induced Rat Model of Parkinson's Disease is Mediated by α7-Nicotinic Receptors

Parkinson’s disease (PD) is a common neurodegenerative disorder, characterized by selective degeneration of dopaminergic nigrostriatal neurons. Most of the existing pharmacological approaches in PD consider replenishing striatal dopamine. It has been reported that activation of the cholinergic system has neuroprotective effects on dopaminergic neurons, and human α7-nicotinic acetylcholine receptor (α7-nAChR) stimulation may offer a potential therapeutic approach in PD. Our recent in-vitro studies demonstrated that curcumin causes significant potentiation of the function of α7-nAChRs expressed in Xenopus oocytes. In this study, we conducted in vivo experiments to assess the role of the α7-nAChR on the protective effects of curcumin in an animal model of PD. Intra-striatal injection of 6-hydroxydopmine (6-OHDA) was used to induce Parkinsonism in rats. Our results demonstrated that intragastric curcumin treatment (200 mg/kg) significantly improved the abnormal motor behavior and offered neuroprotection against the reduction of dopaminergic neurons, as determined by tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra and caudoputamen. The intraperitoneal administration of the α7-nAChR-selective antagonist methyllycaconitine (1 µg/kg) reversed the neuroprotective effects of curcumin in terms of both animal behavior and TH immunoreactivity. In conclusion, this study demonstrates that curcumin has a neuroprotective effect in a 6-hydroxydopmine (6-OHDA) rat model of PD via an α7-nAChR-mediated mechanism.

Measurement of natural variation of neurotransmitter tissue content in red harvester ant brains among different colonies

Colonies of the red harvester ant, Pogonomyrmex barbatus, regulate foraging activity based on food availability and local conditions. Colony variation in foraging behavior is thought to be linked to biogenic amine signaling and metabolism. Measurements of differences in neurotransmitters have not been made among ant colonies in a natural environment. Here, for the first time, we quantified tissue content of 4 biogenic amines (dopamine, serotonin, octopamine, and tyramine) in single forager brains from 9 red harvester ant colonies collected in the field. Capillary electrophoresis coupled with fast-scan cyclic voltammetry (CE-FSCV) was used to separate and detect the amines in individual ant brains. Low levels of biogenic amines were detected using field-amplified sample stacking by preparing a single brain tissue sample in acetonitrile and perchloric acid. The method provides low detection limits: 1 nM for dopamine, 2 nM for serotonin, 5 nM for octopamine, and 4 nM for tyramine. Overall, the content of dopamine (47 ± 9 pg/brain) was highest, followed by octopamine (36 ± 10 pg/brain), serotonin (20 ± 4 pg/brain), and tyramine (14 ± 3 pg/brain). Relative standard deviations were high, but there was less variation within a colony than among colonies, so the neurotransmitter content of each colony might change with environmental conditions. This study demonstrates that CE-FSCV is a useful method for investigating natural variation in neurotransmitter content in single ant brains and could be useful for future studies correlating tissue content with colony behavior such as foraging. Graphical abstract.

Crucial Role of Dopamine D2 Receptor Signaling in Nicotine-Induced Conditioned Place Preference

Nicotine in tobacco causes psychological dependence through its rewarding effect in the central nervous system (CNS). Although nicotine dependence is explained by dopamine receptor (DR) signaling together with nicotinic acetylcholine receptors (nAChRs), the synaptic molecular mechanism underlying the interaction between dopamine receptor and nAChRs remains unclear. Since reward signaling is mediated by dopamine receptors, we hypothesized that the dopamine D2 receptor (D2R), in part, mediates the synaptic modulation of nicotine-induced conditioned place preference (CPP) in addition to dopamine D1 receptor. To investigate the involvement of D2R, wild-type (WT) and dopamine D2 receptor knockout (D2RKO) mice were assessed using the CPP task after induction of nicotine-induced CPP. As expected, D2RKO mice failed to induce CPP behaviors after repeated nicotine administration (0.5 mg/kg). When kinase signaling was assessed in the nucleus accumbens and hippocampal CA1 region after repeated nicotine administration, both Ca²⁺/calmodulin-dependent protein kinase (CaMKII) and extracellular signal-regulated kinase (ERK) were upregulated in WT mice but not in D2RKO mice. Likewise, nicotine-induced CPP was associated with elevation of pro- brain-derived neurotropic factor (BDNF) and BDNF protein levels in WT mice, but not in D2RKO mice. Taken together, in addition to dopamine D1 receptor signaling, dopamine D2 receptor signaling is critical for induction of nicotine-induced CPP in mice.

The novel pesticide flupyradifurone (Sivanto) affects honeybee motor abilities

Honeybees and other pollinators are threatened by changing landscapes and pesticides resulting from intensified agriculture. In 2018 the European Union prohibited the outdoor use of three neonicotinoid insecticides due to concerns about pollinators. A new pesticide by the name of "Sivanto" was recently released by Bayer AG. Its active ingredient flupyradifurone binds to the nicotinic acetylcholine receptor (AchR) in the honeybee brain, similar to neonicotinoids. Nevertheless, flupyradifurone is assumed to be harmless for honeybees and can even be applied on flowering crops. So far, only little has been known about sublethal effects of flupyradifurone on honeybees. Intact motor functions are decisive for numerous behaviors including foraging and dancing. We therefore selected a motor assay to investigate in how far sublethal doses of this pesticide affect behavior in young summer and long-lived winter honeybees. Our results demonstrate that flupyradifurone (830 µmol/l) can evoke motor disabilities and disturb normal motor behavior after a single oral administration (1.2 µg/bee). These effects are stronger in long-lived winter bees than in young summer bees. After offering an equal amount of pesticide (1.0-1.75 µg) continuously over 24 h with food the observed effects are slighter. For comparisons we repeated our experiments with the neonicotinoid imidacloprid. Intriguingly, the alterations in behavior induced by this pesticide (4 ng/bee) were different and longer-lasting compared to flupyradifurone, even though both substances bind to nicotinic acetylcholine receptors.

Electrochemical Measurements of Acetylcholine-Stimulated Dopamine Release in Adult Drosophila melanogaster Brains

The fruit fly, Drosophila melanogaster, is a popular model organism for studying neurological processes and diseases due to the availability of sophisticated genetic tools. While endogenous neurotransmitter release has been characterized in Drosophila larvae, here, we measured endogenous dopamine release in isolated adult Drosophila brains for the first time. Dopamine was measured with fast-scan cyclic voltammetry (FSCV), and acetylcholine or nicotine were used as the stimulus, as both interact with nicotinic acetylcholine receptors (nAChRs) to evoke endogenous dopamine release. Stimulations with 10 pmol of acetylcholine elicited 0.26 ± 0.05 μM dopamine, while 70 fmol nicotine stimulations evoked 0.29 ± 0.03 μM in the central complex. Nicotine-stimulated dopamine release lasted much longer than acetylcholine-stimulated release. Dopamine release is reduced in the presence of nAChR antagonist α-bungarotoxin and the sodium channel blocker tetrodotoxin, indicating release is mediated by nAChRs and exocytosis. The identity of dopamine was confirmed by using 3-iodotyrosine, a dopamine synthesis inhibitor, and by confirming that release was not changed in octopamine synthesis mutant flies, Tdc2 RO54. Additionally, the half-decay time ( t50) in fumin (67 ± 15 s), dopamine transporter mutant flies, was larger than in wild-type flies (16 ± 3.7 s) further proving that acetylcholine stimulation evokes dopamine release. This study demonstrates that stimulation of nAChRs can be used to elicit endogenous dopamine release in adult fly brains, which will be a useful technique for future studies probing dopamine changes during aging or in neurodegenerative diseases.

Nanomaterials-Based Electrochemical Sensors for In Vitro and In Vivo Analyses of Neurotransmitters

Neurotransmitters are molecules that transfer chemical signals between neurons to convey messages for any action conducted by the nervous system. All neurotransmitters are medically important; the detection and analysis of these molecules play vital roles in the diagnosis and treatment of diseases. Among analytical strategies, electrochemical techniques have been identified as simple, inexpensive, and less time-consuming processes. Electrochemical analysis is based on the redox behaviors of neurotransmitters, as well as their metabolites. A variety of electrochemical techniques are available for the detection of biomolecules. However, the development of a sensing platform with high sensitivity and selectivity is challenging, and it has been found to be a bottleneck step in the analysis of neurotransmitters. Nanomaterials-based sensor platforms are fascinating for researchers because of their ability to perform the electrochemical analysis of neurotransmitters due to their improved detection efficacy, and they have been widely reported on for their sensitive detection of epinephrine, dopamine, serotonin, glutamate, acetylcholine, nitric oxide, and purines. The advancement of electroanalytical technologies and the innovation of functional nanomaterials have been assisting greatly in in vivo and in vitro analyses of neurotransmitters, especially for point-of-care clinical applications. In this review, firstly, we focus on the most commonly employed electrochemical analysis techniques, in conjunction with their working principles and abilities for the detection of neurotransmitters. Subsequently, we concentrate on the fabrication and development of nanomaterials-based electrochemical sensors and their advantages over other detection techniques. Finally, we address the challenges and the future outlook in the development of electrochemical sensors for the efficient detection of neurotransmitters.

Drosophila as a Model System for Neurotransmitter Measurements

Drosophila melanogaster, the fruit fly, is an important, simple model organism for studying the effects of genetic mutations on neuronal activity and behavior. Biologists use Drosophila for neuroscience studies because of its genetic tractability, complex behaviors, well-known and simple neuroanatomy, and many orthologues to human genes. Neurochemical measurements in Drosophila are challenging due to the small size of the central nervous system. Recently, methods have been developed to measure real-time neurotransmitter release and clearance in both larvae and adults using electrochemistry. These studies have characterized dopamine, serotonin, and octopamine release in both wild type and genetic mutant flies. Tissue content measurements are also important, and separations are predominantly used. Capillary electrophoresis, with either electrochemical, laser-induced fluorescence, or mass spectrometry detection, facilitates tissue content measurements from single, isolated Drosophila brains or small samples of hemolymph. Neurochemical studies in Drosophila have revealed that flies have functioning transporters and autoreceptors, that their metabolism is different than in mammals, and that flies have regional, life stage, and sex differences in neurotransmission. Future studies will develop smaller electrodes, expand optical imaging techniques, explore physiological stimulations, and use advanced genetics to target single neuron release or study neurochemical changes in models of human diseases.