The cognitive and behavioral effects of D-amphetamine and nicotine sensitization in adult zebrafish

Metabolic clues to memory loss: High-fat diets and brain-adipose crosstalk in zebrafish

Obesity is a growing public health concern that significantly impacts cognitive functions, including memory. This research explores how a high-fat diet affects short-term memory, employing the novel object recognition (NOR) test and NMR-based metabolomics to elucidate metabolic alterations in the brain and adipose tissue. The zebrafish were divided into two groups: one receiving a standard diet (SD) and the other a high-fat diet (HFD). Body mass index (BMI) was assessed every two weeks for a period of eight weeks. The NOR test was used to determine the discrimination index (DI) for evaluating the short-term memory of the SD and HFD groups. NMR spectroscopy was employed to investigate the metabolites in brain and adipose tissues, and multivariate data analysis was conducted to discover significant metabolic alterations. The high-fat diet (HFD) resulted in a significant increase in body mass index (BMI) (p < 0.0001) compared to the standard diet (SD) group from week 4 to week 8. A significant reduction in the discrimination index (24.95 %) in the HFD group against the SD group suggests a decline in memory performance among HFD subjects. NMR-based metabolomics of adipose tissue revealed that linoleic acid and caprylic acid were consistently found to exhibit increased levels in the HFD group across all assessments, whereas lauric acid, ALA, EPA, and DHA were consistently present at elevated levels in the adipose tissue of the SD group. NMR-based metabolomics of the brain identified GABA, taurine, and histamine as the key metabolites distinguishing the HFD from the SD group in female zebrafish. For male zebrafish brains, taurine, phenylalanine, and tryptophan were identified as the most significant metabolites for differentiating between HFD and SD. These metabolites demonstrated a notable decrease in the HFD group relative to the SD group. The results of this study align with those of previously reported studies in rodents and humans, indicating that memory impairment associated with obesity may stem from neuroinflammation and changes in synaptic plasticity. This research provides insights into the molecular changes in adipose tissue and the brain that occur when individuals receive a high-fat diet (HFD), which may enhance our understanding of the link between obesity and memory impairment, ultimately leading to a better comprehension of the disease.

Neurotranscriptomic and behavioral effects of ISRIB, and its therapeutic effects in the traumatic brain injury model in zebrafish

Traumatic brain injury (TBI) is a global medical concern and has a lasting impact on brain activity with high risks of mortality. Current treatments are inadequate for repairing damaged brain cells or correcting cognitive and behavioral disabilities in TBI patients. Mounting evidence links TBI to the activation of the Integrated Stress Response (ISR) signaling in the brain. A novel small molecule, ISRIB, is an effective inhibitor of the ISR pathway, offering potential advantages for brain health. Here, we investigated how ISRIB affects brain transcriptome and behavior in zebrafish TBI model evoked by telencephalic brain injury. Overall, while TBI diminished memory and social behavior in zebrafish, administering ISRIB post-injury markedly reduced these behavioral deficits, and modulated brain gene expression, rescuing TBI-activated pathways related to inflammation and brain cell development. Collectively, this supports the role of brain ISR in TBI, and suggests potential utility of ISRIB for the treatment of TBI-related states.

Transient cognitive impacts of oxygen deprivation caused by catch-and-release angling

Vertebrate brain function is particularly sensitive to the effects of hypoxia, with even brief periods of oxygen deprivation causing significant brain damage and impaired cognitive abilities. This study is the first to investigate the cognitive consequences of hypoxia in fish, specifically induced by exhaustive exercise and air exposure, conditions commonly encountered during catch-and-release (C&R) practices in recreational fishing. Angling exerts substantial pressure on inland fish populations, underscoring the need for sustainable practices like C&R. While C&R survival rates are generally high, understanding its sublethal impacts is crucial for evaluating the practice's ethical and ecological sustainability. We examined the effects of these stressors on the cognitive function of 238 rainbow trout, using the free movement pattern Y-maze method to assess working memory through navigational search patterns during free exploration sessions. Our results showed that air exposure led to short-term (3-4 h post-treatment), but transient impairments in working memory, with no long-term cognitive deficits observed at one week and one month post-treatment. These findings emphasize the high tolerance of fish to hypoxia and support the sustainability of C&R as a tool in fisheries management.

Zebrafish models for studying cognitive enhancers

Cognitive decline is commonly seen both in normal aging and in neurodegenerative and neuropsychiatric diseases. Various experimental animal models represent a valuable tool to study brain cognitive processes and their deficits. Equally important is the search for novel drugs to treat cognitive deficits and improve cognitions. Complementing rodent and clinical findings, studies utilizing zebrafish (Danio rerio) are rapidly gaining popularity in translational cognitive research and neuroactive drug screening. Here, we discuss the value of zebrafish models and assays for screening nootropic (cognitive enhancer) drugs and the discovery of novel nootropics. We also discuss the existing challenges, and outline future directions of research in this field.

Ontogeny of working memory and behavioural flexibility in the free movement pattern (FMP) Y-maze in zebrafish

The acquisition of executive skills such as working memory, decision-making and adaptive responding occur at different stages of central nervous system development. Zebrafish (Danio rerio) are increasingly used in behavioural neuroscience for complex behavioural tasks, and there is a critical need to understand the ontogeny of their executive functions. Zebrafish across developmental stages (4, 7, 14, 30 and 90 days post fertilisation (dpf)), were assessed to track development of working memory (WM) and behavioural flexibility (BF) using the free movement pattern Y-maze (FMP Y-maze). Several differences in both WM and BF were identified during the transition from yolk-dependent to independent feeding. Specifically, WM is evident in all age groups, even from 4 dpf. However, BF is not developed until larvae start free feeding, and show significant improvement thereafter, with young adults (90 dpf) demonstrating the most well-defined BF. We demonstrate, for the first time, objective WM processes in 4 dpf zebrafish larvae. This suggests that those wishing to study WM in zebrafish may be able to do so from 4 dpf, thus drastically increasing throughput. In addition, we show that zebrafish follow distinct stages of cognitive development and age-related changes during the early developmental period. Finally, our findings indicate distinct WM and BF mechanisms, which may be useful to study for translational purposes.

Advances in Zebrafish as a Comprehensive Model of Mental Disorders

As an important part in international disease, mental disorders seriously damage human health and social stability, which show the complex pathogenesis and increasing incidence year by year. In order to analyze the pathogenesis of mental disorders as soon as possible and to look for the targeted drug treatment for psychiatric diseases, a more reasonable animal model is imperious demands. Benefiting from its high homology with the human genome, its brain tissue is highly similar to that of humans, and it is easy to realize whole-body optical visualization and high-throughput screening; zebrafish stands out among many animal models of mental disorders. Here, valuable qualified zebrafish mental disorders models could be established through behavioral test and sociological analysis, which are simulated to humans, and combined with molecular analyses and other detection methods. This review focuses on the advances in the zebrafish model to simulate the human mental disorders; summarizes the various behavioral characterization means, the use of equipment, and operation principle; sums up the various mental disorder zebrafish model modeling methods; puts forward the current challenges and future development trend, which is to contribute the theoretical supports for the exploration of the mechanisms and treatment strategies of mental disorders.

Behavioral profile of adult zebrafish acutely exposed to a selective dopamine uptake inhibitor, GBR 12909

BACKGROUND

The dopamine transporter (DAT) is the main regulator of dopamine concentration in the extrasynaptic space. The pharmacological inhibition of the DAT results in a wide spectrum of behavioral manifestations, which have been identified so far in a limited number of species, mostly in rodents.

AIM

Here, we used another well-recognized model organism, the zebrafish (Danio rerio), to explore the behavioral effects of GBR 12909, a highly-affine selective DAT blocker.

METHODS

We evaluated zebrafish locomotion, novelty-related exploration, spatial cognition, and social phenotypes in the novel tank, habituation and shoaling tests, following acute 20-min water immersion in GBR 12909.

RESULTS

Our findings show hypolocomotion, anxiety-like state, and impaired spatial cognition in fish acutely treated with GBR 12909. This behavioral profile generally parallels that of the DAT knockout rodents and zebrafish, and it overlaps with behavioral effects of other DAT-inhibiting drugs of abuse, such as cocaine and D-amphetamine.

CONCLUSION

Collectively, our data support the utility of zebrafish in translational studies on DAT targeting neuropharmacology and strongly implicate DAT aberration as an important mechanisms involved in neurological and psychiatric diseases.

Neuroprotective Effects of Phytochemicals against Aluminum Chloride-Induced Alzheimer’s Disease through ApoE4/LRP1, Wnt3/β-Catenin/GSK3β, and TLR4/NLRP3 Pathways with Physical and Mental Activities in a Rat Model

Background: Alzheimer’s disease (AD) is a neurodegenerative disorder that is associated with abnormal cognition. AD is aided in its initiation and progression by hereditary and environmental factors. Aluminum (Al) is a neurotoxic agent that causes oxidative stress, which is linked to AD progression. Additionally, Nrf2/HO-1, APOE4/LRP1, Wnt3/β-catenin, and TLR4/NLRP3 are the main signaling pathways involved in AD pathogenesis. Several phytochemicals are promising options in delaying AD evolution. Objectives: This study aimed at studying the neuroprotective effects of some phytochemicals as morin (MOR), thymol (TML), and thymoquinone (TMQ) on physical and mental activities (PhM) in Al chloride (AlCl₃)-induced AD rat model. Another objective was to determine the specificity of phytochemicals to AD signaling pathways using molecular docking. Methods: Eighty male Dawley rats were divided into eight groups. Each group received: saline (control group), AlCl₃, (ALAD), PhM, either alone or with a combination of MOR, TML, and/or TMQ for five weeks. Animals were then subjected to behavioral evaluation. Brain tissues were used for histopathological and biochemical analyses to determine the extent of neurodegeneration. The effect of phytochemicals on AlCl₃-induced oxidative stress and the main signaling pathways involved in AD progression were also investigated. Results: AlCl₃ caused a decline in spatial learning and memory, as well as histopathological changes in the brains of rats. Phytochemicals combined with PhM restored antioxidant activities, increased HO-1 and Nrf2 levels, blocked inflammasome activation, apoptosis, TLR4 expression, amyloide-β generation, and tau hyperphophorylation. They also brought ApoE4 and LRP1 levels back to normal and regulated Wnt3/β-catenin/GSK3β signaling pathway. Conclusions: The use of phytochemicals with PhM is a promising strategy for reducing AD by modulating Nrf2/HO-1, TLR4/NLRP3, APOE4/LRP1, and Wnt3/β-catenin/GSK-3β signaling pathways.

Modelling Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) Using Mice and Zebrafish

Autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD) are two debilitating neurodevelopmental disorders. The former is associated with social impairments whereas the latter is associated with inattentiveness, hyperactivity, and impulsivity. There is recent evidence that both disorders are somehow related and that genes may play a large role in these disorders. Despite mounting human and animal research, the neurological pathways underlying ASD and ADHD are still not well understood. Scientists investigate neurodevelopmental disorders by using animal models that have high similarities in genetics and behaviours with humans. Mice have been utilized in neuroscience research as an excellent animal model for a long time; however, the zebrafish has attracted much attention recently, with an increasingly large number of studies using this model. In this review, we first discuss ASD and ADHD aetiology from a general point of view to their characteristics and treatments. We also compare mice and zebrafish for their similarities and discuss their advantages and limitations in neuroscience. Finally, we summarize the most recent and existing research on zebrafish and mouse models of ASD and ADHD. We believe that this review will serve as a unique document providing interesting information to date about these models, thus facilitating research on ASD and ADHD.

The Brilliance of the Zebrafish Model: Perception on Behavior and Alzheimer's Disease

Alzheimer's disease (AD) has become increasingly prevalent in the elderly population across the world. It's pathophysiological markers such as overproduction along with the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFT) are posing a serious challenge to novel drug development processes. A model which simulates the human neurodegenerative mechanism will be beneficial for rapid screening of potential drug candidates. Due to the comparable neurological network with humans, zebrafish has emerged as a promising AD model. This model has been thoroughly validated through research in aspects of neuronal pathways analogous to the human brain. The cholinergic, glutamatergic, and GABAergic pathways, which play a role in the manifested behavior of the zebrafish, are well defined. There are several behavioral models in both adult zebrafish and larvae to establish various aspects of cognitive impairment including spatial memory, associative memory, anxiety, and other such features that are manifested in AD. The zebrafish model eliminates the shortcomings of previously recognized mammalian models, in terms of expense, extensive assessment durations, and the complexity of imaging the brain to test the efficacy of therapeutic interventions. This review highlights the various models that analyze the changes in the normal behavioral patterns of the zebrafish when exposed to AD inducing agents. The mechanistic pathway adopted by drugs and novel therapeutic strategies can be explored via these behavioral models and their efficacy to slow the progression of AD can be evaluated.

Interactions between cigarette smoking and cognitive status on functional connectivity of the cortico-striatal circuits in individuals without dementia: A resting-state functional MRI study

Aims

Cigarette smoking is a modifiable risk factor for Alzheimer's disease (AD), and controlling risk factors may curb the progression of AD. However, the underlying neural mechanisms of the effects of smoking on cognition remain largely unclear. Therefore, we aimed to explore the interaction effects of smoking × cognitive status on cortico‐striatal circuits, which play a crucial role in addiction and cognition, in individuals without dementia.

Methods

We enrolled 304 cognitively normal (CN) non‐smokers, 44 CN smokers, 130 mild cognitive impairment (MCI) non‐smokers, and 33 MCI smokers. The mixed‐effect analysis was performed to explore the interaction effects between smoking and cognitive status (CN vs. MCI) based on functional connectivity (FC) of the striatal subregions (caudate, putamen, and nucleus accumbens [NAc]).

Results

The significant interaction effects of smoking × cognitive status on FC of the striatal subregions were detected in the left inferior parietal lobule (IPL), bilateral cuneus, and bilateral anterior cingulate cortex (ACC). Specifically, increased FC of right caudate to left IPL was found in CN smokers compared with non‐smokers. The MCI smokers showed decreased FC of right caudate to left IPL and of right putamen to bilateral cuneus and increased FC of bilateral NAc to bilateral ACC compared with CN smokers and MCI non‐smokers. Furthermore, a positive correlation between FC of the NAc to ACC with language and memory was detected in MCI smokers.

Conclusions

Cigarette smoking could affect the function of cortico‐striatal circuits in patients with MCI. Our findings suggest that quitting smoking in the prodromal stage of AD may have the potential to prevent disease progression.

Behavioral and Gene Regulatory Responses to Developmental Drug Exposures in Zebrafish

Developmental consequences of prenatal drug exposure have been reported in many human cohorts and animal studies. The long-lasting impact on the offspring-including motor and cognitive impairments, cranial and cardiac anomalies and increased prevalence of ADHD-is a socioeconomic burden worldwide. Identifying the molecular changes leading to developmental consequences could help ameliorate the deficits and limit the impact. In this study, we have used zebrafish, a well-established behavioral and genetic model with conserved drug response and reward pathways, to identify changes in behavior and cellular pathways in response to developmental exposure to amphetamine, nicotine or oxycodone. In the presence of the drug, exposed animals showed altered behavior, consistent with effects seen in mammalian systems, including impaired locomotion and altered habituation to acoustic startle. Differences in responses seen following acute and chronic exposure suggest adaptation to the presence of the drug. Transcriptomic analysis of exposed larvae revealed differential expression of numerous genes and alterations in many pathways, including those related to cell death, immunity and circadian rhythm regulation. Differential expression of circadian rhythm genes did not correlate with behavioral changes in the larvae, however, two of the circadian genes, arntl2 and per2, were also differentially expressed at later stages of development, suggesting a long-lasting impact of developmental exposures on circadian gene expression. The immediate-early genes, egr1, egr4, fosab, and junbb, which are associated with synaptic plasticity, were downregulated by all three drugs and in situ hybridization showed that the expression for all four genes was reduced across all neuroanatomical regions, including brain regions implicated in reward processing, addiction and other psychiatric conditions. We anticipate that these early changes in gene expression in response to drug exposure are likely to contribute to the consequences of prenatal exposure and their discovery might pave the way to therapeutic intervention to ameliorate the long-lasting deficits.