Locomotor Activity Of Zebrafish Larvae Research Articles

Sleep deprivation effects on EGFR signaling in a zebrafish exposed to rotenone

The objective of this study was to investigate the effects of exposure to rotenone, sleep deprivation, and the epidermal growth factor receptor (EGFR) inhibitor on the locomotor activity of zebrafish larvae. Observations were conducted on control groups, sleep-deprived groups without interventions, groups treated with rotenone or the EGFR inhibitor alone, and also groups with combined exposures. The results showed that sleep deprivation alone led to a decrease of speed of the locomotor activity compared to the control groups. The treatment with rotenone alone resulted in varied effects on the locomotor activity. However, a combined exposure to rotenone and sleep deprivation further reduced the locomotor activity compared to the control and rotenone-treated groups. The groups treated with the EGFR inhibitor alone exhibited variable effects on the locomotor activity. Furthermore, the combined exposure to the EGFR inhibitor and sleep deprivation resulted in diverse changes in the locomotor activity. However, the combined treatment with rotenone and the EGFR inhibitor produced complex alterations in the locomotor activity.These findings demonstrate the distinct effects of exposure to rotenone, sleep deprivation, and the EGFR inhibitor on the locomotor activity of zebrafish larvae. The interaction between these factors further modulates locomotor activity, suggesting a potential interplay between the EGFR system, sleep regulation, and the dopaminergic system. Understanding the relationship between the EGFR system, sleep regulation, and neurological regulation may contribute to the development of therapeutic strategies to address such issues as sleep disorders and neurodegenerative conditions.

Realistic microplastics harness bacterial presence and promote impairments in early zebrafish embryos: Behavioral, developmental, and transcriptomic approaches.

The plastisphere is a newly recognized ecosystem. However, its interaction with early life stages of aquatic vertebrates is a multifaceted issue that requires further research. This study investigated the involvement of bacteria in shaping realistic microplastics hazards in zebrafish Danio rerio embryos. Fish were exposed to bottle micro-fragments (FR) and textile micro-fibers (FI) of polyethylene terephthalate (5–15 μm), concomitant with Aeromonas salmonicida achromogenes challenge from 2h post-fertilization for 3 days. Egg chorion showed affinity for FR and FI, inducing earlier embryo hatching. However, this effect was masked by biofilm invasion. Fragments were more detrimental than fibers on developmental parameters, while bacterial presence compromised body length, eye, and yolk sac surface area. In a further finding, MPs alone increased locomotor activity in zebrafish larvae, without synergistic effect when combined with bacteria. Data showed that realistic MPs had no significant effects except for downregulated sod and cyp1a gene expression, whereas bacterial challenge inhibited larval potency for most of the evaluated mRNA levels (mpx (immune system), apoeb (lipid metabolism), nfkb and tfa (inflammation), cyp and sod (oxidative stress)). This study provides new insights into realistic microplastic effects under relevant conditions when combined with environmental pathogen within the first life stages of aquatic vertebrates.

Developmental toxicity, immunotoxicity and cardiotoxicity induced by methidathion in early life stages of zebrafish

Methidathion is a highly effective organophosphorus pesticide and is extensively utilized for the control of insects in agricultural production. However, there is little information on the adverse effects and underlying mechanisms of methidathion on aquatic organisms. In this work, embryonic zebrafish were exposed to methidathion at concentrations of 4, 10, and 25 mg/L for 96 h, and morphological changes and activities of antioxidant indicators alterations were detected. In addition, the locomotor behavioral abilities of zebrafish exposed to methidathion were also measured. To further explore the mechanism of the toxic effects of methidathion, gene expression levels associated with cardiac development, cell apoptosis, and the immune system were tested through qPCR assays. The findings revealed that methidathion exposure could induce a decrease in survival rate, hatchability, length of body, and increase in abnormality of zebrafish, as well as cardiac developmental toxicity. The LC50 value of methidathion in zebrafish embryos was determined to be about 30.72 mg/L at 96 hpf. Additionally, methidathion exposure triggered oxidative stress in zebrafish by increasing SOD activity, ROS, and MDA content. Acridine orange (AO) staining indicated that methidathion exposure led to apoptosis, which was mainly distributed in the pericardial region. Furthermore, significant impairments of locomotor activity in zebrafish larvae were induced by methidathion exposure. Lastly, the expression of pro-inflammatory factors including IFN-γ, IL-6, IL-8, CXCL-clc, TLR4, and MYD88 significantly up-regulated in exposed zebrafish. Taken together, the results in this work illustrated that methidathion caused developmental toxicity, cardiotoxicity, and immunotoxicity in embryogenetic zebrafish.

Effects of Pregnanolone Glutamate and Its Metabolites on GABAA and NMDA Receptors and Zebrafish Behavior.

Multiple molecular targets have been identified to mediate membrane-delimited and nongenomic effects of natural and synthetic steroids, but the influence of steroid metabolism on neuroactive steroid signaling is not well understood. To begin to address this question, we set out to identify major metabolites of a neuroprotective synthetic steroid 20-oxo-5β-pregnan-3α-yl l-glutamyl 1-ester (pregnanolone glutamate, PAG) and characterize their effects on GABAA and NMDA receptors (GABARs, NMDARs) and their influence on zebrafish behavior. Gas chromatography-mass spectrometry was used to assess concentrations of PAG and its metabolites in the hippocampal tissue of juvenile rats following intraperitoneal PAG injection. PAG is metabolized in the peripheral organs and nervous tissue to 20-oxo-17α-hydroxy-5β-pregnan-3α-yl l-glutamyl 1-ester (17-hydroxypregnanolone glutamate, 17-OH-PAG), 3α-hydroxy-5β-pregnan-20-one (pregnanolone, PA), and 3α,17α-dihydroxy-5β-pregnan-20-one (17-hydroxypregnanolone, 17-OH-PA). Patch-clamp electrophysiology experiments in cultured hippocampal neurons demonstrate that PA and 17-OH-PA are potent positive modulators of GABARs, while PAG and 17-OH-PA have a moderate inhibitory effect at NMDARs. PAG, 17-OH-PA, and PA diminished the locomotor activity of zebrafish larvae in a dose-dependent manner. Our results show that PAG and its metabolites are potent modulators of neurotransmitter receptors with behavioral consequences and indicate that neurosteroid-based ligands may have therapeutic potential.

Graphene quantum dots (GQDs) induce thigmotactic effect in zebrafish larvae via modulating key genes and metabolites related to synaptic plasticity

Graphene quantum dots (GQDs) recently gain much attention for its medicinal values in treating diseases such as neurodegeneration and inflammations. However, owing to the high permeability of GQDs across the blood-brain barrier, whether its retention in the central nervous system (CNS) perturbs neurobehaviors remains less reported. In the study, the locomotion of zebrafish larvae (Danio rerio) was fully evaluated when administrated by two GQDs in a concentration gradient, respectively as reduced-GQDs (R-GQDs): 150, 300, 600, 1200, and 2400 g/L, and graphene oxide QDs (GOQDs): 60, 120, 240, 480, and 960 g/L. After exposure, the larvae were kept for locomotion analysis within one week’s depuration. Substantial data showed that the basal locomotor activity of zebrafish larvae was not significantly changed by both two GQDs at low concentrations while weakened greatly with the increase of concentrations, and the total ATP levels of zebrafish larvae were also found to decrease significantly when exposed to the highest concentrations of GQDs. Next, the thigmotactic effect was observed to be remarkably induced in larvae by both two GQDs at any concentrations during exposure, and remained strong in larvae treated by high concentrations of R-GQDs after 7 days’ depuration. To be noted, we found that GQDs affected the synaptic plasticity via downregulating the mRNA levels of NMDA and AMPA receptor family members as well as the total glutamine levels in zebrafish larvae. Together, our study presented robust data underlying the locomotor abnormalities aroused by GQDs in zebrafish larvae and indicated the potential adverse effects of GQDs on synaptic plasticity.

Inflammation as a target for the treatment of fever-associated epilepsy in zebrafish larvae

Inflammation is considered to be involved in epileptogenesis. However, the relationship between fever and inflammation as well as the mechanisms of fever in the occurrence and development of childhood epilepsy need further investigation. Here, we described an in vivo model of hyperthermia-induced seizures in zebrafish larvae with pentylenetetrazole (PTZ) exposure. Hyperthermia increased the susceptibility to seizure and the production of pro-inflammatory factors in PTZ-induced zebrafish larvae. As mutations in GABRG2 have been associated with fever-associated epilepsy, we used a Tg(hGABRG2F343L) zebrafish model expressing mutant human GABRG2(F343L) to further investigate the involvement of inflammation in fever-induced seizures. Our data indicated that hyperthermia also increased the locomotor activity in Tg(hGABRG2F343L) zebrafish larvae. Although the production of pro-inflammatory factors was upregulated by GABRG2 mutation, hyperthermia did not change the production of pro-inflammatory factors significantly. Lipopolysaccharide (LPS) stimulation was sufficient to increase the locomotor activity in zebrafish larvae, suggesting that inflammation contributed to fever-associated epilepsy. The expression of GABRG2 was increased with PTZ induction, especially at a higher temperature. Moreover, inhibition of inflammation by dexamethasone (DEX) reduced the excitability of zebrafish larvae, especially at a higher temperature. Finally, in vitro experiments proved that LPS stimulation increased the production of IL-1β and IL-6 in GABRG2(F343L) transfected cells. Collectively, our study demonstrated that neuroinflammation was induced in febrile seizures, and the increased expression of IL-1β and IL-6 might be responsible for epileptogenesis. The vicious cycle between fever and inflammation might induce seizure onset, and anti-inflammatory strategies might be a potential treatment for fever-associated epilepsy.

Modulation of sleep behavior in zebrafish larvae by pharmacological targeting of the orexin receptor

New pharmacological approaches that target orexin receptors (OXRs) are being developed to treat sleep disorders such as insomnia and narcolepsy, with fewer side effects than existing treatments. Orexins are neuropeptides that exert excitatory effects on postsynaptic neurons via the OXRs, and are important in regulating sleep/wake states. To date, there are three FDA-approved dual orexin receptor antagonists for the treatment of insomnia, and several small molecule oral OX2R (OXR type 2) agonists are in the pipeline for addressing the orexin deficiency in narcolepsy. To find new hypnotics and psychostimulants, rodents have been the model of choice, but they are costly and have substantially different sleep patterns to humans. As an alternative model, zebrafish larvae that like humans are diurnal and show peak daytime activity and rest at night offer several potential advantages including the ability for high throughput screening. To pharmacologically validate the use of a zebrafish model in the discovery of new compounds, we aimed in this study to evaluate the functionality of a set of known small molecule OX2R agonists and antagonists on human and zebrafish OXRs and to probe their effects on the behavior of zebrafish larvae. To this end, we developed an in vitro IP-One Homogeneous Time Resolved Fluorescence (HTRF) immunoassay, and in vivo locomotor assays that record the locomotor activity of zebrafish larvae under physiological light conditions as well as under dark-light triggers. We demonstrate that the functional IP-One test is a good predictor of biological activity in vivo. Moreover, the behavioral data show that a high-throughput assay that records the locomotor activity of zebrafish throughout the evening, night and morning is able to distinguish between OXR agonists and antagonists active on the zebrafish OXR. Conversely, a locomotor assay with alternating 30min dark-light transitions throughout the day is not able to distinguish between the two sets of compounds, indicating the importance of circadian rhythm to their pharmacological activity. Overall, the results show that a functional IP-one test in combination with a behavioral assay using zebrafish is well-suited as a discovery platform to find novel compounds that target OXRs for the treatment of sleep disorders.

2, 5-dichloro-1, 4-benuinone exposure to zebrafish embryos/larvae causes neurodevelopmental toxicity

2, 5-dichloro-1, 4-benuinone (2, 5-DCBQ) is an emerging disinfection by-product belonging to the class of halobenzoquinones (HBQs). However, there is limited evidence regarding the neurotoxic effects of 2, 5-DCBQ. To better understand the toxicological mechanisms of aquatic organisms, zebrafish embryos were exposed to 0.2 mg/L, 0.4 mg/L, and 0.6 mg/L of 2, 5-DCBQ from 4 h post-fertilization (hpf) to 120 hpf. Developmental defects, such as reduced body length, decreased heart rate, decreased pigmentation, and abnormal motor axon structure was observed. In particular, the locomotor activity of zebrafish larvae reduced with exposure to increasing 2, 5-DCBQ concentrations, and this effect was more pronounced under dark stimulation. The results indicated that the genes associated with neuronal development (gfap, mbp, syn2a, elavl3, ache, and a1-tubulin) were significantly downregulated after treatment with 2, 5-DCBQ. Furthermore, the KEGG result showed the neuroactive ligand-receptor interaction and apoptosis pathways were visibly disrupted, and we found acetylcholinesterase activity was also affected. In summary, the disinfection by-product, 2, 5-DCBQ, exhibits neurodevelopmental toxicity in zebrafish embryos, providing novel evidence for comprehensive analyses of its toxicity.

Elevated photic response is followed by a rapid decay and depressed state in ictogenic networks.

The switch between nonseizure and seizure states involves profound alterations in network excitability and synchrony. In this study, we aimed to identify and compare features of neural excitability and dynamics across multiple zebrafish seizure and epilepsy models. Inspired by video-electroencephalographic recordings in patients, we developed a framework to study spontaneous and photically evoked neural and locomotor activity in zebrafish larvae, by combining high-throughput behavioral tracking and whole-brain in vivo two-photon calcium imaging. Our setup allowed us to dissect behavioral and physiological features that are divergent or convergent across multiple models. We observed that spontaneous locomotor and neural activity exhibit great diversity across models. Nonetheless, during photic stimulation, hyperexcitability and rapid response dynamics were well conserved across multiple models, highlighting the reliability of photically evoked activity for high-throughput assays. Intriguingly, in several models, we observed that the initial elevated photic response is often followed by rapid decay of neural activity and a prominent depressed state. Elevated photic response and following depressed state in seizure-prone networks are significantly reduced by the antiseizure medication valproic acid. Finally, rapid decay and depression of neural activity following photic stimulation temporally overlap with slow recruitment of astroglial calcium signals that are enhanced in seizure-prone networks. We argue that fast decay of neural activity and depressed states following photic response are likely due to homeostatic mechanisms triggered by excessive neural activity. An improved understanding of the interplay between elevated and depressed excitability states might suggest tailored epilepsy therapies.

The effect of centella asiatica extract in Zebrafish (Danio rerio) larvae as a Chronic Constant Hypoxia (CCH) model

Backgound: Chronic Constan Hypoxia (CCH) are able to occur in cyanotic congenital heart disease and bronchopulmonary dysplasia (BPD). Centella asiatica has antioxidant and neuroprotective effects in experimental animals.This study aims to observe the effect of Centella asiatica ethanol extract on Zebrafish in chronic hypoxic conditions
 Method: A laboratory experimental study with a randomized post-test controlled group design was conducted among 20 Zebrafish (Danio rerio) 3-8 day post fertilization (dpf) as samples per tube. The total group treatment was five with inclusion and exclusion criterias. Variables assessed in this study included Average body length, locomotor activity, and the relationship between average body length and locomotor activity. Data were analyzed using SPSS version 18 for Windows.
 Result: There was a moderate significant correlation between Centella asiatica concentration of 1.25 µg/ml, 2.5 µg/ml, 5 µg/ml with an enhancement of body length (r=0.431) and locomotor activity (r=0.262) in zebrafish larvae CCH model (p<0.05).
 Conclusion: It can be concluded that chronic constan hypoxia (CCH) inhibit the growth of body length and decrease locomotor activity in Zebrafish larvae. Centella asiatica treatment can avoid the CCH by using various concentration.

Early detection of cyanide, organophosphate and rodenticide pollution based on locomotor activity of zebrafish larvae.

Cyanide, organophosphate and rodenticides are highly toxic substances widely used in agriculture and industry. These toxicants are neuro- and organotoxic to mammals at low concentrations, thus early detection of these chemicals in the aqueous environment is of utmost importance. Here, we employed the behavioral toxicity test with wildtype zebrafish larvae to determine sublethal concentrations of the above mentioned common environmental pollutants. After optimizing the test with cyanide, nine rodenticides and an organophosphate were successfully tested. The compounds dose-dependently initially (0–60-min exposure) stimulated locomotor activity of larvae but induced toxicity and reduced swimming during 60–120-min exposure. IC50 values calculated based on swimming distance after 2-h exposure, were between 0.1 and 10 mg/L for both first-generation and second-generation anticoagulant rodenticides. Three behavioral characteristics, including total distance travelled, sinuosity and burst count, were quantitatively analyzed and compared by hierarchical clustering of the effects measured by each three parameters. The toxicity results for all three behavioral endpoints were consistent, suggesting that the directly measured parameter of cumulative swimming distance could be used as a promising biomarker for the aquatic contamination. The optimized method herein showed the potential for utilization as part of a monitoring system and an ideal tool for the risk assessment of drinking water in the military and public safety.

Avobenzone and nanoplastics affect the development of zebrafish nervous system and retinal system and inhibit their locomotor behavior

The use of cosmetics is growing with each passing day, arousing widespread attention to their ingredients. Avobenzone (AVO) and nanoplastics (NPs) are typical ingredients in cosmetics, which coexist in the aquatic environment and have a combined effect on aquatic organisms. In this study, the accumulation of AVO and NPs in zebrafish larvae and effects on gene expression and enzymatic activity related to nervous functions, and locomotor behavior were investigated. AVO and NPs accumulated continuously in zebrafish, and the combined exposure enhanced AVO accumulation. After recovery, the accumulated concentrations of AVO and NPs in zebrafish remained unchanged, suggesting that AVO and NPs could not be eliminated in 72 h. The genes regulated nervous system development were affected mainly by AVO exposure, while the genes regulated retinal system development were affected by NPs exposure. Single and combined exposures of AVO and NPs affected the activities of acetylcholinesterase and antioxidant enzymes in zebrafish, and superoxide dismutase activity could not return to normal level after 72 h of recovery period. The locomotor activity of zebrafish larvae was significantly inhibited by AVO and NPs, which might be related to the alterations in functions of nervous system development and retinal system development as well as the interference of neurotransmitter system and antioxidant system.

Bis (2-ethylhexyl)-2,3,4,5-tetrabromophthalate showed poor penetrability but increased the permeability of blood brain barrier: Evidences from in vitro and in vivo studies

Bis(2ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a replacement for restricted flame retardants, has become ubiquitous in the environment. To reveal the neurotoxicity and underlying mechanism of TBPH, we first evaluated its penetrability through the blood-brain barrier (BBB) using hCMEC/D3 cells as in vitro model, and found TBPH had poor penetrability through BBB with a maximum Papp of 14.8 × 10−6 cms−1. Further study using transgenetic zebrafish (Tg flk1: EGFP) as in vivo model confirmed that TBPH could affect the BBB permeability, probably via affecting the transcription of genes encoding tight junction proteins. Finally, wild type zebrafish embryos/larvae were exposed to TBPH to evaluate the neurotoxicity. The neurodevelopment, neurotransmitters and locomotor activity of zebrafish larvae did not changed, which may be because TBPH can hardly cross the BBB to pose direct exposure to the central nervous system. However, the transcription of opsins genes and visual response to light stimulation in zebrafish larvae were inhibited, pointing to additional mechanism that may cause visual impairment indirectly. Above all, these results can help further understand the neurotoxicity and underlying mechanism by TBPH, and also pointed out potential risk of this chemical to aquatic organisms.

Estrogen receptor: A potential linker of estrogenic and dopaminergic pathways in zebrafish larvae following deltamethrin exposure

Deltamethrin (DM), a type II pyrethroid insecticide, is widely used to control agricultural pests. However, its excessive use exerts a detrimental effect on the ecological environment and human health, indicating the need to study its potential risks in detail. In the present study, zebrafish embryos were exposed to varying concentrations of DM (0.1, 1, 10, and 25 μg/L) for 96 h to assess the alterations in the transcript levels of proteins of the estrogenic and dopaminergic pathways. In addition, its effect on zebrafish locomotor activity was studied. The mRNA expression of cyp19a1b, erα, erβ2, fshr, gnrh2, gnrhr3, vtg3, dat, and dr1 significantly changed after exposing the embryos to DM. Deltamethrin at 10 and 25 μg/L significantly reduced the average swimming speed of zebrafish larvae. In addition, embryos injected with zebrafish estrogen receptor α (erα) and β (erβ) morpholinos and co-exposed to 25 μg/L DM for 96 h showed reduced expression of vtg3 mRNA compared to embryos exposed to 25 μg/L DM only. The locomotor activity of erα and erβ knockdown zebrafish following DM exposure was increased significantly when compared with that of larvae exposed to 25 μg/L DM only. Our results demonstrated that DM altered the locomotor activity of zebrafish larvae and the transcript levels of the components of estrogenic and dopaminergic pathways; erα and erβ knockdown weakened these effects.

Tralopyril affects locomotor activity of zebrafish (Danio rerio) by impairing tail muscle tissue, the nervous system, and energy metabolism

Tralopyril (TP), an antifouling biocide, is widely used to prevent heavy biofouling, and can have potential risks to aquatic organisms. In this study, the effect of TP on locomotor activity and related mechanisms were evaluated in zebrafish (Danio rerio) larvae. TP significantly reduced locomotor activity after 168 -h exposure. Adverse modifications in tail muscle tissue, the nervous system, and energy metabolism were also observed in larvae. TP caused thinning of the muscle bundle in the tail of larvae. In conjunction with the metabolomics results, changes in dopamine (DA) and acetylcholine (ACh), acetylcholinesterase (AChE) activity, and the expression of genes involved in neurodevelopment, indicate that TP may disrupt the nervous system in zebrafish larvae. The change in metabolites (e.g., glucose 6-phosphate, cis-Aconitic acid, acetoacetyl-CoA, coenzyme-A and 3-Oxohexanoyl-CoA) involved in carbohydrate and lipid metabolism indicates that TP may disrupt energy metabolism. TP exposure may inhibit the locomotor activity of zebrafish larvae by impairing tail muscle tissue, the nervous system, and energy metabolism.

Antidepressant Screening Demonstrated Non-Monotonic Responses to Amitriptyline, Amoxapine and Sertraline in Locomotor Activity Assay in Larval Zebrafish.

Antidepressants are well-known drugs to treat depression and major depressive disorder for humans. However, the misuse and abuse of antidepressants keep increasing with several side effects reported. The aim of this study was to assess the potential adverse effects of 18 antidepressants by monitoring zebrafish larval locomotor activity performance based on the total distance traveled, burst movement count, and total rotation count at four dark-light intercalated phases. In general, zebrafish larvae displayed sedative effects after antidepressant exposure by showing a significant reduction in all of the locomotor activity-related endpoints. However, three antidepressants i.e., amitriptyline, amoxapine, and sertraline were able to trigger a significantly high locomotor activity in zebrafish larvae during the light cycle. These differences might be due to the pharmacologic differences among the antidepressants. In addition, since each antidepressant possesses a different dosage range from the other, overdoses of these antidepressants might also be the causes of these differences. Furthermore, based on these results, a further study was conducted to observe the effect of these three antidepressants in lower concentrations. From the results, biphasic effects in terms of zebrafish larval locomotor activity were demonstrated by these drugs. Even though further studies are still required to validate the mechanism, these findings indicate that these antidepressants might share a common mechanism responsible for their effects on zebrafish larval locomotor activity although there were some differences in potency of these effects.

The Histamine System in Zebrafish Brain: Organization, Receptors, and Behavioral Roles.

Three of the four histamine receptors have been identified in zebrafish. Whereas only one histamine receptor 1 gene (hrh1) is known, two copies of histamine receptor 2 (hrh2a and hrh2b) have been identified. Although initially only one gene encoding for histamine receptor 3 (hrh3) was recognized in zebrafish, the genome database contains information for two more hrh3-like genes, whereas no genes corresponding for histamine receptor 4 with expression mainly in the immune system have been identified. Hrh1 and hrh3 show prominent uneven expression in the zebrafish brain, with the strongest expression in the dorsal telencephalon. Quantitatively significant expression of hrh1, hrh2, and hrh3 can also be found in several peripheral organs. Whereas antagonists of hrh1, hrh2, and hrh3 all affect the locomotor activity of zebrafish larvae, interpretation of the data is hampered by a lack of information on receptor binding and signaling characteristics. Zebrafish mutants lacking any of the three histamine receptors have shown modest behavioral phenotypes, possibly due to genetic compensation. None of the receptor mutant fish have shown significant sleep phenotypes. Adult zebrafish lacking hrh3 display decreased locomotor activity. The zebrafish histamine system shows significant life-long plasticity: presenilin 1 mutant zebrafish develop an abnormally large number of histamine neurons and increased thigmotaxis and anxiety-related phenotype. Overexpression of histidine decarboxylase (hdc) in larval zebrafish is associated with an increased number of hypocretin neurons, whereas translation inhibition of hdc or exposure to α-fluoromethylhistidine leads to decreased numbers of hypocretin neurons. Current pharmacological evidence suggests that this may be mediated by hrh1. Further studies using acute, e.g., pharmacogenetic or optogenetic manipulation of selected components of brain circuits, are required to understand the full range of physiological functions of zebrafish histamine receptors.

Polystyrene nanoparticles trigger the activation of p38 MAPK and apoptosis via inducing oxidative stress in zebrafish and macrophage cells.

Polystyrene nanoparticles (PS NPs), originated from breakdown of large plastic wastes, have already caused much concern for their environmental risks on health. This current study was aimed to reveal the toxicological mechanism of PS NPs on developing zebrafish and macrophage cells. To fulfill this purpose, 42nmPS NPs were exposed to the early development stage of zebrafish for 5 days, the decreased heart rate and locomotor activity of zebrafish larvae were observed. The fluorescent PS NPs were used to precisely assess the accumulation of PS NPs in zebrafish larvae, and the results indicated that PS NPs not only accumulated in digestive system, but also infiltrated into the liver. More importantly, the transcriptomic analysis revealed that a total of 356 genes were differentially expressed and the KEGG class map showed significant differences in the MAPK pathway upon PS NPs treatment. Meanwhile, the induction of oxidative stress and inflammation were also observed in zebrafish larvae. Furthermore, PS NPs also induced oxidative damage and inflammatory response in RAW 264.7 cells, which activated p38 MAPK signal pathway and finally induced cell apoptosis. Our study provides a new understanding of MAPK signaling pathway involved in toxicity mechanism.

Ethanol affects behavior and HPA axis activity during development in zebrafish larvae

Recent studies have shown that long-term alcohol intake from food can lead to numerous mental disorders in humans, and the social and health effects of excessive intake of alcohol currently represent serious problems for governments and families worldwide. However, to date, it has not been determined how alcohol affects the hypothalamic–pituitary–adrenal (HPA) axis. The zebrafish offers a good model for studying the toxicology of food-grade ethanol. In the present study, using zebrafish larvae exposed to 1% ethanol, we performed zebrafish behavioral analysis. Samples were collected for enzyme-linked immunosorbent assay (ELISA) and quantitative real time-polymerase chain reaction (qRT-PCR) experiments, and statistical analysis was performed. We found that ethanol decreased the locomotor activity of zebrafish larvae, which showed a more intense reaction to external stimuli. Ethanol also increased the level of HPA axis hormones in zebrafish larvae, influenced the level of neurotransmitters, and altered the expression of key genes in neurotransmitter metabolism. Ethanol exposure affects zebrafish behavior, increases the level of HPA axis hormones in zebrafish larvae, affects the level of neurotransmitters, and affects the expression of key genes in dopamine and serotonin metabolism. These findings may help to elucidate the effects of ethanol on HPA axis activity.

Impacts of bisphenol A analogues on zebrafish post-embryonic brain.

Bisphenol A (BPA) is a widely studied and well-recognised endocrine-disrupting chemical, and one of the current issues is its safe replacement by various analogues. Using larva zebrafish as a model, the present study reveals that moderate and chronic exposure to BPA analogues such as bisphenol S, bisphenol F and bisphenol AF may also affect vertebrate neurodevelopment and locomotor activity. Several parameters of embryo-larval development were investigated, such as mortality, hatching, number of mitotically active cell, as defined by 5-bromo-2'-deoxyuridine incorporation and proliferative cell nuclear antigen labelling, aromatase B protein expression in radial glial cell and locomotor activity. Our results show that exposure to several bisphenol analogues induced an acceleration of embryo hatching rate. At the level of the developing brain, a strong up-regulation of the oestrogen-sensitive Aromatase B was also detected in the hypothalamic region. This up-regulation was not associated with effects on the numbers of mitotically active progenitors nor differentiated neurones in the preoptic area and in the nuclear recessus posterior of the hypothalamus zebrafish larvae. Furthermore, using a high-throughput video tracking system to monitor locomotor activity in zebrafish larvae, we show that some bisphenol analogues, such as bisphenol AF, significantly reduced locomotor activity following 6days of exposure. Taken together, our study provides evidence that BPA analogues can also affect the neurobehavioural development of zebrafish.