Postsynaptic receptors regulate presynaptic transmitter stability through transsynaptic bridges.

Stable matching of neurotransmitters with their receptors is fundamental to synapse function and reliable communication in neural circuits. Presynaptic neurotransmitters regulate the stabilization of postsynaptic transmitter receptors. Whether postsynaptic receptors regulate stabilization of presynaptic transmitters has received less attention. Here, we show that blockade of endogenous postsynaptic acetylcholine receptors (AChR) at the neuromuscular junction destabilizes the cholinergic phenotype in motor neurons and stabilizes an earlier, developmentally transient glutamatergic phenotype. Further, expression of exogenous postsynaptic gamma-aminobutyric acid type A receptors (GABAA receptors) in muscle cells stabilizes an earlier, developmentally transient GABAergic motor neuron phenotype. Both AChR and GABAA receptors are linked to presynaptic neurons through transsynaptic bridges. Knockdown of specific components of these transsynaptic bridges prevents stabilization of the cholinergic or GABAergic phenotypes. Bidirectional communication can enforce a match between transmitter and receptor and ensure the fidelity of synaptic transmission. Our findings suggest a potential role of dysfunctional transmitter receptors in neurological disorders that involve the loss of the presynaptic transmitter.

Phospholipids Differentially Regulate Ca2+ Binding to Synaptotagmin-1.

Synaptotagmin-1 (Syt-1) is a calcium sensing protein that is resident in synaptic vesicles. It is well established that Syt-1 is essential for fast and synchronous neurotransmitter release. However, the role of Ca2+ and phospholipid binding in the function of Syt-1, and ultimately in neurotransmitter release, is unclear. Here, we investigate the binding of Ca2+ to Syt-1, first in the absence of lipids, using native mass spectrometry to evaluate individual binding affinities. Syt-1 binds to one Ca2+ with a KD ∼ 45 µM. Each subsequent binding affinity (n ≥ 2) is successively unfavorable. Given that Syt-1 has been reported to bind anionic phospholipids to modulate the Ca2+ binding affinity, we explored the extent that Ca2+ binding was mediated by selected anionic phospholipid binding. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and dioleoylphosphatidylserine (DOPS) positively modulated Ca2+ binding. However, the extent of Syt-1 binding to phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) was reduced with increasing [Ca2+]. Overall, we find that specific lipids differentially modulate Ca2+ binding. Given that these lipids are enriched in different subcellular compartments and therefore may interact with Syt-1 at different stages of the synaptic vesicle cycle, we propose a regulatory mechanism involving Syt-1, Ca2+, and anionic phospholipids that may also control some aspects of vesicular exocytosis.

[Improvement effect of cinnamaldehyde on reserpine-induced Parkinson's disease rat model].

In order to study the neuroprotective mechanism of cinnamaldehyde on reserpine-induced Parkinson's disease(PD) rat models, 72 male Wistar rats were randomly divided into blank group, model group, Madopar group, and cinnamaldehyde high-, medium-, and low-dose groups. Except for the blank group, the other groups were intraperitoneally injected with reserpine of 0.1 mg·kg~(-1) once every other morning, and cinnamaldehyde and Madopar solutions were gavaged every afternoon. Open field test, rotarod test, and oral chewing movement evaluation were carried out in the experiment. The brain was taken and fixed. The positive expression of dopamine receptor D1(DRD1) was detected by TSA, and the changes in neurotransmitters such as dopamine(DA) and 3,4-dihydroxyphenylacetic acid(DOPAC) in the brain were detected by enzyme-linked immunosorbent assay(ELISA). The protein and mRNA expression levels of tyrosine hydroxylase(TH) and α-synuclein(α-Syn) in substantia nigra(SN) were detected by RT-PCR and Western blot. The results showed that after the injection of reserpine, the hair color of the model group became yellow and dirty; the arrest behavior was weakened, and the body weight was reduced. The spontaneous movement and exploration behavior were reduced, and the coordination exercise ability was decreased. The number of oral chewing was increased, but the cognitive ability was decreased, and the proportion of DRD1 positive expression area in SN was decreased. The expression of TH protein and mRNA was down-regulated, and that of α-Syn protein and mRNA was up-regulated. After cinnamaldehyde intervention, it had an obvious curative effect on PD model animals. The spontaneous movement behavior, the time of staying in the rod, the time of movement, the distance of movement, and the number of standing times increased, and the number of oral chewing decreased. The proportion of DRD1 positive expression area in SN increased, and the protein and mRNA expression levels of α-Syn were down-regulated. The protein and mRNA expression levels of TH were up-regulated. In addition, the levels of DA, DOPAC, and homovanillic acid(HVA) neurotransmitters in the brain were up-regulated. This study can provide a new experimental basis for clinical treatment and prevention of PD.

Protein-Based Tools for Studying Neuromodulation.

Neuromodulators play crucial roles in regulating neuronal activity and affecting various aspects of brain functions, including learning, memory, cognitive functions, emotional states, and pain modulation. In this Account, we describe our group's efforts in designing sensors and tools for studying neuromodulation. Our lab focuses on developing new classes of integrators that can detect neuromodulators across the whole brain while leaving a mark for further imaging analysis at high spatial resolution. Our lab also designed chemical- and light-dependent protein switches for controlling peptide activity to potentially modulate the endogenous receptors of the neuromodulatory system in order to study the causal effects of selective neuronal pathways.

Different states of synaptic vesicle priming explain target cell type-dependent differences in neurotransmitter release.

Pronounced differences in neurotransmitter release from a given presynaptic neuron, depending on the synaptic target, are among the most intriguing features of cortical networks. Hippocampal pyramidal cells (PCs) release glutamate with low probability to somatostatin expressing oriens-lacunosum-moleculare (O-LM) interneurons (INs), and the postsynaptic responses show robust short-term facilitation, whereas the release from the same presynaptic axons onto fast-spiking INs (FSINs) is ~10-fold higher and the excitatory postsynaptic currents (EPSCs) display depression. The mechanisms underlying these vastly different synaptic behaviors have not been conclusively identified. Here, we applied a combined functional, pharmacological, and modeling approach to address whether the main difference lies in the action potential-evoked fusion or else in upstream priming processes of synaptic vesicles (SVs). A sequential two-step SV priming model was fitted to the peak amplitudes of unitary EPSCs recorded in response to complex trains of presynaptic stimuli in acute hippocampal slices of adult mice. At PC-FSIN connections, the fusion probability (Pfusion) of well-primed SVs is 0.6, and 44% of docked SVs are in a fusion-competent state. At PC-O-LM synapses, Pfusion is only 40% lower (0.36), whereas the fraction of well-primed SVs is 6.5-fold smaller. Pharmacological enhancement of fusion by 4-AP and priming by PDBU was recaptured by the model with a selective increase of Pfusion and the fraction of well-primed SVs, respectively. Our results demonstrate that the low fidelity of transmission at PC-O-LM synapses can be explained by a low occupancy of the release sites by well-primed SVs.

[Research progress on the neural mechanism of the regulation of social isolation on innate behaviors].

Innate behavior is mainly controlled by genetics, but is also regulated by social experiences such as social isolation. Studies in animal models such as Drosophila and mice have found that social isolation can regulate innate behaviors through the changes at the molecular level, such as hormone, neurotransmitter, neuropeptide level, and at the level of neural circuits. In this review, we summarized the research progress on the regulation of social isolation on various animal innate behaviors, such as sleep, reproduction and aggression by altering the expression of conserved neuropeptides and neurotransmitters, hoping to deepen the understanding of the key and conserved signal pathways that regulate innate behavior by social isolation.

Parental exposure to antidepressants has lasting effects on offspring? A case study with zebrafish.

Fish have common neurotransmitter pathways with humans, exhibiting a significant degree of conservation and homology. Thus, exposure to fluoxetine makes fish potentially susceptible to biochemical and physiological changes, similarly to what is observed in humans. Over the years, several studies demonstrated the potential effects of fluoxetine on different fish species and at different levels of biological organization. However, the effects of parental exposure to unexposed offspring remain largely unknown. The consequences of 15-day parental exposure to relevant concentrations of fluoxetine (100 and 1000 ng/L) were assessed on offspring using zebrafish as a model organism. Parental exposure resulted in offspring early hatching, non-inflation of the swimming bladder, increased malformation frequency, decreased heart rate and blood flow, and reduced growth. Additionally, a significant behavioral impairment was also found (reduced startle response, basal locomotor activity, and altered non-associative learning during early stages and a negative geotaxis and scototaxis, reduced thigmotaxis, and anti-social behavior at later life stages). These behavior alterations are consistent with decreased anxiety, a significant increase in the expression of the monoaminergic genes slc6a4a (sert), slc6a3 (dat), slc18a2 (vmat2), mao, tph1a, and th2, and altered levels of monoaminergic neurotransmitters. Alterations in behavior, expression of monoaminergic genes, and neurotransmitter levels persisted until offspring adulthood. Given the high conservation of neuronal pathways between fish and humans, data show the possibility of potential transgenerational and multigenerational effects of pharmaceuticals' exposure. These results reinforce the need for transgenerational and multigenerational studies in fish, under realistic scenarios, to provide realistic insights into the impact of these pharmaceuticals.

Miniaturized Implantable Fluorescence Probes Integrated with Metal-Organic Frameworks for Deep Brain Dopamine Sensing.

Continuously monitoring neurotransmitter dynamics can offer profound insights into neural mechanisms and the etiology of neurological diseases. Here, we present a miniaturized implantable fluorescence probe integrated with metal-organic frameworks (MOFs) for deep brain dopamine sensing. The probe is assembled from physically thinned light-emitting diodes (LEDs) and phototransistors, along with functional surface coatings, resulting in a total thickness of 120 µm. A fluorescent MOF that specifically binds dopamine is introduced, enabling a highly sensitive dopamine measurement with a detection limit of 79.9 nM. A compact wireless circuit weighing only 0.85 g is also developed and interfaced with the probe, which was later applied to continuously monitor real-time dopamine levels during deep brain stimulation in rats, providing critical information on neurotransmitter dynamics. Cytotoxicity tests and immunofluorescence analysis further suggest a favorable biocompatibility of the probe for implantable applications. This work presents fundamental principles and techniques for integrating fluorescent MOFs and flexible electronics for brain-computer interfaces and may provide more customized platforms for applications in neuroscience, disease tracing, and smart diagnostics.

Chrysin for Neurotrophic and Neurotransmitter Balance in Parkinson's Disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has a direct impact on the dopaminergic neurons in the substantia nigra pars compacta (SNpc), dopamine in the striatum (ST), homovanillic acid (HVA), neurotrophic factors of the SNpc, and ST regions leading to Parkinson's disease (PD). Dopaminergic neuron atrophy in the SNpc and dopamine degradation in the ST have an explicit link to disrupted homeostasis of the neurotrophic factor brain-derived neurotrophic factor (BDNF) of the SNpc and ST regions. Chrysin is a flavonoid with a pharmacological potential that directly influences neurotrophic levels as well as neurotransmitters. As a result, analysis of the altering levels of neurotransmitters such as dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), are observed via high-performance liquid chromatography (HPLC) and the confirmation of the influential role of BDNF and glial-derived neurotrophic factor (GDNF) in the homeostasis of dopamine, DOPAC, and HAV via examination of gene expression. The observation confirmed that chrysin balances the altering levels of neurotransmitters as well as neurotrophic factors. The protocols for reverse transcription-polymerase chain reaction (RT-PCR) and HPLC analysis for neurotransmitter levels from the SNpc and ST regions of acute PD mice brain-induced MPTP are described in this chapter.

Microbiome and its impact on fetal and neonatal brain development: current opinion in pediatrics.

PURPOSE OF REVIEW: Emerging evidence suggests that the gut microbiota and its metabolites regulate neurodevelopment and cognitive functioning via a bi-directional communication system known as the microbiota-gut-brain axis (MGBA). RECENT FINDINGS: The MGBA influences brain development and function via the hypothalamic-pituitary axis, the vagal nerve, immune signaling, bacterial production of neurotransmitters, and microbial metabolites like short-chain fatty acids, tryptophan derivatives, and bile acids. Animal studies show fetal neurodevelopment is mediated by maternal microbiota derivatives, immune activation, and diet. Furthermore, manipulation of the microbiota during critical windows of development, like antibiotic exposure and fecal microbiota transplantation, can affect cognitive functioning and behavior in mice. Evidence from human studies, particularly in preterm infants, also suggests that a disrupted gut microbiota colonization may negatively affect neurodevelopment. Early microbial signatures were linked to favorable and adverse neurodevelopmental outcomes. SUMMARY: The link between the gut microbiota and the brain is evident. Future studies, including experimental studies, larger participant cohort studies with longitudinal analyses of microbes, their metabolites, and neurotransmitters, and randomized controlled trials are warranted to further elucidate the mechanisms of the MGBA. Identification of early, predictive microbial markers could pave the way for the development of novel early microbiota-based intervention strategies, such as targeted probiotics, and vaginal or fecal microbiota transplantation, aimed at improving infant neurodevelopment.

Perspectives on the impact of vortioxetine on the treatment armamentarium of major depressive disorder.

INTRODUCTION: Major Depressive Disorder (MDD) is a mental health issue that significantly affects patients' quality of life and functioning. Despite available treatments, many patients continue to suffer due to incomplete symptom resolution and side effects. AREAS COVERED: This manuscript examines Vortioxetine's role in Major Depressive Disorder (MDD) treatment, highlighting its potential to reshape therapeutic strategies due to its unique Multimodal action and proven broad-spectrum efficacy in multiple depressive domains. A detailed examination of Vortioxetine's pharmacological aspects, including indications, dosage, pharmacodynamics, and pharmacokinetics, is provided, emphasizing its safety and effectiveness. The discussion extends to Vortioxetine's role in acute-phase treatment and maintenance of MDD and its profound impact on specialized depression domains. EXPERT OPINION: Vortioxetine is distinguished for its novel multimodal serotonin modulation mechanism, showcasing significant promise as an innovative treatment for MDD. Its efficacy, which is dose-dependent, along with a commendable tolerability profile, positions it as a potential leading option for initial treatment strategies. The discourse on dosage titration, particularly the strategy of initiating treatment at lower doses followed by gradual escalation, underscores the approach toward minimizing initial adverse effects while optimizing therapeutic outcomes, aligning with the principles of personalized medicine in psychiatric care.

Switching on generalized fear.

Stress induces a neurotransmitter switch that leads to fear in harmless situations.

Huanglian-banxia promotes gastric motility of diabetic rats by modulating brain-gut neurotransmitters through MAPK signaling pathway.

BACKGROUND: Gastric motility disorder is an increasingly common problem among people with diabetes. Neurotransmitters have been recognized as critical regulators in the process of gastric motility. Previous study has shown that herb pair huanglian-banxia (HL-BX) can improve gastric motility, but the underlying mechanism is still unclear. The aim of this study was to further investigate the role of HL-BX in modulating brain-gut neurotransmission to promote gastric motility in diabetic rats, and to explore its possible mechanism. METHODS: The diabetic rats were divided into five groups. Gastric emptying rate, intestinal propulsion rate, body weight, and average food intake were determined. Substance P (SP), 5- hydroxytryptamine (5-HT), and glucagon-like peptide -1 (GLP-1) in the serum were measured by enzyme-linked immunosorbent assay. Dopamine (DA) and norepinephrine (NE) in the brain were analyzed by high-pressure liquid chromatography with a fluorescence detector. Protein expression of the tissues in the stomach and brain was determined by Western blot. KEY RESULTS: HL-BX reduced average food intake significantly, increased body weight, and improved gastric emptying rate and intestinal propulsion rate. HL-BX administration caused a significant increase in SP, GLP-1, and 5-HT, but a significant decrease in DA and NE. Interestingly, HL-BX regulated simultaneously the different expressions of MAPK and its downstream p70S6K/S6 signaling pathway in the stomach and brain. Moreover, berberine exhibited a similar effect to HL-BX. CONCLUSIONS: These results indicated that HL-BX promoted gastric motility by regulating brain-gut neurotransmitters through the MAPK signaling pathway. HL-BX and MAPK provide a potential therapeutic option for the treatment of gastroparesis.

Environmentally relevant exposure to cotinine induces neurobehavioral toxicity in zebrafish (Danio rerio): A study using neurobehavioral and metabolomic approaches.

As an important psychoactive substance, cotinine is ubiquitous in aquatic environment and poses a threat to aquatic organisms. However, the mechanism of its adverse health impacts remains unclear. We evaluated the effects of cotinine exposure at environmentally relevant concentrations on the development and locomotor behavior of zebrafish (Danio rerio) larvae using neurotransmitters and whole endogenous metabolism. Mild developmental toxicity and significant neurobehavior disorder, such as spontaneous movement (1-1000 µg/L), 48 hpf tactile response (50, 100, and 1000 µg/L), and 144 hpf swimming speed (1, 10, 100, 500, and 1000 µg/L), were observed in zebrafish. Exposure to cotinine led to significant alterations in 11 neurotransmitters, including homogentisic acid, serotonin, glutamic acid and aspartic acid, etc. 298 metabolites were identified and two pathways - linoleic acid metabolism and taurine and hypotaurine metabolism - were delineated. In addition, amino acid neurotransmitters were significantly correlated with metabolites such as arachidonic acid as well as its derivatives, steroidal compounds, and amino acids. Serotonin demonstrates a noteworthy correlation with 31 out of 40 differentially expressed neurotransmitters, encompassing lipids, amino acids, and other compounds. These novel findings contribute to a comprehensive understanding of the ecological risks associated with cotinine contamination in surface waters.

α1 and ß3 adrenergic receptor-mediated excitatory effects of adrenaline on the caudal neurosecretory system (CNSS) in olive flounder, Paralichthys olivaceus.

Adrenaline is one of the most important neurotransmitters in the central nervous system and is produced during stress. In this study, we investigated the modulatory role of adrenaline and adrenergic receptors on the neuroendocrine Dahlgren cells in the caudal neurosecretory system (CNSS) of olive flounder. Ex vivo electrophysiological recordings revealed that adrenaline significantly increased the firing frequency and altered the firing pattern of Dahlgren cells. Moreover, treatment with adrenaline led to a significant upregulation of ion channels and major hormone secretion genes in CNSS at the mRNA levels. Additionally, treatment with adrenaline resulted in a significantly elevation in the expression levels of α1- and ß3-adrenergic receptors. Furthermore, the ß3-adrenergic receptor antagonist exerts a significant inhibitory effect on adrenaline-induced enhancement firing activities of Dahlgren cells, whereas the α1-adrenergic receptor antagonist displays a comparatively weaker inhibitory effect. Additionally, the enhanced firing activity induced by adrenaline could be effectively suppressed by both α1- and ß3-adrenergic receptor antagonists. Taken together, these findings provide strong evidence in favor of the excitatory effects of adrenaline through α1 and ß3 adrenergic receptors in CNSS to stimulate the secretion of stress-related hormones, ß3-adrenergic receptor plays a more dominant role in the modulation of firing activities of Dahlgren cells by adrenaline and thereby regulates the stress response in olive flounder.

Long-term exposure to 6-PPD quinone at environmentally relevant concentrations causes neurotoxicity by affecting dopaminergic, serotonergic, glutamatergic, and GABAergic neuronal systems in Caenorhabditis elegans.

6-PPD quinone (6-PPDQ), an emerging environmental pollutant, is converted based on 6-PPD via ozonation. However, a systematic evaluation on possible neurotoxicity of long-term and low-dose 6-PPDQ exposure and the underlying mechanism remain unknown. In the present work, 0.1-10 µg/L 6-PPDQ was added to treat Caenorhabditis elegans for 4.5 days, with locomotion behavior, neuronal development, sensory perception behavior, neurotransmitter content, and levels of neurotransmission-related genes being the endpoints. 6-PPDQ exposure at 0.1-10 µg/L significantly reduced locomotion behavior, and that at 1-10 µg/L decreased sensory perception behavior in nematodes. Moreover, 6-PPDQ exposure at 10 µg/L notably induced damage to the development of dopaminergic, glutamatergic, serotonergic, and GABAergic neurons. Importantly, nematodes with chronic 6-PPDQ exposure at 10 µg/L were confirmed to suffer obviously decreased dopamine, serotonin, glutamate, dopamine, and GABA contents and altered neurotransmission-related gene expression. Meanwhile, the potential binding sites of 6-PPDQ and neurotransmitter synthesis-related proteins were further shown by molecular docking method. Lastly, Pearson's correlation analysis showed that locomotion behavior and sensory perception behavior were positively correlated with the dopaminergic, serotonergic, glutamatergic, and GABAergic neurotransmission. Consequently, 6-PPDQ exposure disturbed neurotransmitter transmission, while such changed molecular foundation for neurotransmitter transmission was related to 6-PPDQ toxicity induction. The present work sheds new lights on the mechanisms of 6-PPDQ and its possible neurotoxicity to organisms at environmentally relevant concentrations.

olf413 an octopamine biogenesis pathway gene is required for axon growth and pathfinding during embryonic nervous system development in Drosophila melanogaster.

OBJECTIVE: Neurotransmitters have been extensively studied as neural communication molecules. Genetic associations discovered, and indirect intervention studies in Humans and mammals have led to a general proposition that neurotransmitters have a role in structuring of neuronal network during development. olf413 is a Drosophila gene annotated as coding for dopamine beta-monooxygenase enzyme with a predicted function in octopaminergic pathway. The biological function of this gene is very little worked out. In this study we investigate the requirement of olf413 gene function for octopamine biogenesis and developmental patterning of embryonic nervous system. RESULT: In our study we have used the newly characterized neuronal specific allele olf413SG1.1, and the gene disruption strain olf413MI02014 to dissect out the function of olf413. olf413 has an enhancer activity as depicted by reporter GFP expression, in the embryonic ventral nerve cord, peripheral nervous system and the somatic muscle bundles. Homozygous loss of function mutants show reduced levels of octopamine, and this finding supports the proposed function of the gene in octopamine biogenesis. Further, loss of function of olf413 causes embryonic lethality. FasII staining of these embryos reveal a range of phenotypes in the central and peripheral motor nerves, featuring axonal growth, pathfinding, branching and misrouting defects. Our findings are important as they implicate a key functional requirement of this gene in precise axonal patterning events, a novel developmental role imparted for an octopamine biosynthesis pathway gene in structuring of embryonic nervous system.

GABAB receptors induce phasic release from medial habenula terminals through activity-dependent recruitment of release-ready vesicles.

GABAB receptor (GBR) activation inhibits neurotransmitter release in axon terminals in the brain, except in medial habenula (MHb) terminals, which show robust potentiation. However, mechanisms underlying this enigmatic potentiation remain elusive. Here, we report that GBR activation on MHb terminals induces an activity-dependent transition from a facilitating, tonic to a depressing, phasic neurotransmitter release mode. This transition is accompanied by a 4.1-fold increase in readily releasable vesicle pool (RRP) size and a 3.5-fold increase of docked synaptic vesicles (SVs) at the presynaptic active zone (AZ). Strikingly, the depressing phasic release exhibits looser coupling distance than the tonic release. Furthermore, the tonic and phasic release are selectively affected by deletion of synaptoporin (SPO) and Ca2+-dependent activator protein for secretion 2 (CAPS2), respectively. SPO modulates augmentation, the short-term plasticity associated with tonic release, and CAPS2 retains the increased RRP for initial responses in phasic response trains. The cytosolic protein CAPS2 showed a SV-associated distribution similar to the vesicular transmembrane protein SPO, and they were colocalized in the same terminals. We developed the "Flash and Freeze-fracture" method, and revealed the release of SPO-associated vesicles in both tonic and phasic modes and activity-dependent recruitment of CAPS2 to the AZ during phasic release, which lasted several minutes. Overall, these results indicate that GBR activation translocates CAPS2 to the AZ along with the fusion of CAPS2-associated SVs, contributing to persistency of the RRP increase. Thus, we identified structural and molecular mechanisms underlying tonic and phasic neurotransmitter release and their transition by GBR activation in MHb terminals.

Acrylamide exposure induces growth retardation, neurotoxicity, stress, and immune/antioxidant disruption in Nile tilapia (Oreochromis niloticus): The alleviative effects of Chlorella vulgaris diets.

This study looked at the toxic impacts of water-born acrylamide (ACR) on Nile tilapia (Oreochromis niloticus) in terms of behaviors, growth, immune/antioxidant parameters and their regulating genes, biochemical indices, tissue architecture, and resistance to Aeromonas hydrophila. As well as the probable ameliorative effect of Chlorella vulgaris (CV) microalgae as a feed additive against ACR exposure was studied. The 96-h lethal concentration 50 of ACR was investigated and found to be 34.67 mg/L for O. niloticus. For the chronic exposure study, a total of 180 healthy O. niloticus (24.33 ± 0.03 g) were allocated into four groups in tri-replicates (15 fish/replicate), C (control) and ACR groups were fed a basal diet and exposed to 0 and 1/10 of 96-h LC50 of ACR (3.46 mg/L), respectively. ACR+ CV5 and ACR+ CV10 groups were fed basal diets with 5 % and 10 % CV supplements, respectively and exposed to 1/10 of 96-h LC50 of ACR for 60 days. After the exposure trial (60 days) the experimental groups were challenged with A. hydrophila. The findings demonstrated that ACR exposure induced growth retardation (P˂0.01) (lower final body weight, body weight gain, specific growth rate, feed intake, protein efficiency ratio, final body length, and condition factor as well as higher feed conversion ratio). A substantial decrease in the immune/antioxidant parameters (P˂0.05) (lysozyme, serum bactericidal activity %, superoxide dismutase, and reduced glutathione) and neurotransmitter (acetylcholine esterase) (P˂0.01) was noticed with ACR exposure. A substantial increase (P˂0.01) in the serum levels of hepato-renal indicators, lipid peroxidation biomarker, and cortisol was noticed as a result of ACR exposure. ACR exposure resulted in up-regulation (P˂0.05) of the pro-inflammatory cytokines and down-regulation (P˂0.05) of the antioxidant-related gene expression. Furthermore, the hepatic, renal, brain, and splenic tissues were badly affected by ACR exposure. ACR-exposed fish were more sensitive to A. hydrophila infection and recorded the lowest survival rate (P˂0.01). Feeding the ACR-exposed fish with CV diets significantly improved the growth and immune/antioxidant status, as well as modulating the hepatorenal functions, stress, and neurotransmitter level compared to the exposed-non fed fish. In addition, modulation of the pro-inflammatory and antioxidant-related gene expression was noticed by CV supplementation. Dietary CV improved the tissue architecture and increased the resistance to A. hydrophila challenge in the ACR-exposed fish. Noteworthy, the inclusion of 10 % CV produced better results than 5 %. Overall, CV diets could be added as a feed supplement in the O. niloticus diet to boost the fish's health, productivity, and resistance to A. hydrophila challenge during ACR exposure.

Effects of butyl paraben on behavior and molecular mechanism of Chinese striped-necked turtle (Mauremys sinensis).

Butyl paraben (BuP) is widely used in cosmetics, drugs, and food preservation. Recently it is an identified new pollutant that affects various aspects of reproduction, lipid metabolism, and nervous system. Behavioral activity serves as a pre-warning biomarker for predicting water quality. So, in this study, the changes in some behaviors and its neurotransmitters and cell apoptosis in the brain of Chinese striped-necked turtles (Mauremys sinensis) were studied when the turtles were exposed to BuP concentrations of 0, 5, 50, 500, and 5000 µg/L for 21 weeks. The results showed that, the basking time and altering scores to external stimuli in the groups of 50, 500, and 5000 µg/L were significantly reduced, while the time for body-righting was significantly increased, compared with the control (0 µg/L), indicating that the turtles exhibited depression and inactive behavior. The analysis of neurotransmitter in the brain showed that 5-hydroxytryptamine (5-HT) contents in the groups of 500 and 5000 µg/L were significantly higher than the other groups, which was due to an increase in the mRNA relative expression levels of the 5-HT receptor gene (5-HTR), neurotransmitter transporter genes (Drd4, Slc6a4), and neurotransmitter synthase tryptophan hydroxylase (TPH). Furthermore, GABA transaminase (GABA-T) activity increased in the 500 and 5000 µg/L groups, and tyrosine hydroxylase (TH) activity increased dramatically in the 5000 µg/L group. However, acetyl-CoA (AChE) activity was significantly reduced in these four BuP exposure groups. These changes could be attributed to decreased movement velocity and increased inactivity. Meanwhile, the mRNA expression level of BAX, Bcl-2, caspase-9 and TUNEL assay indicated the occurrence of cell apoptosis in the brains of the higher BuP exposed groups, which may play an important role in neuronal death inducing behavior change. In summary, these findings offer fundamental insights into turtle ecotoxicology and serve as a foundation for a comprehensive assessment of the ecological and health risks associated with BuP.