Time to (finally) acknowledge that fish have emotionality and pain

The increasing work using fish as a model organism calls for a better understanding of their sentience. While growing evidence suggests that pain and emotionality exist in zebrafish, many deniers continue to ignore the evidence. Here we revisit the main conceptual breakthroughs in the field that argue clearly for pain and emotionality. We call for an end to denial and a focus on studying the mechanisms of fish pain and emotionality, and their translational relevance to human conditions

How zebrafish models are reshaping modern translational neuroscience and drug discovery research

The zebrafish (Danio rerio) is a small freshwater teleost fish that has become a new powerful aquatic vertebrate model organism in preclinical biomedical research and drug screening. Zebrafish possess all major neurotransmitter receptors, transporters and enzymes, as well as express rich behavioral repertoire, thereby offering a wide spectrum of CNS disease models. However, our understanding of zebrafish role as a new emerging mainstream model in neuroscience research is still limited. For example, zebrafish behavior has long been mistakenly viewed as “primitive” or “reflex-driven”, resulting in incomplete utilization of the major advantages of this species for CNS disease modeling or drug discovery – 1) phenotypic robustness, 2) ease of experimental manipulations, 3) high-throughput potential, and 4) high relevance to the 3Rs principles of humane animal experimentation. Here, we will discuss zebrafish models relevant to several important human disorders, including epilepsy, autism, stress/depression, anxiety and addiction, to demonstrate excellent future of this model organism in biological psychiatry research. Furthermore, zebrafish are highly sensitive to all major classes of neurotropic drugs (including antipsychotics, anxiolytics, antidepressants, sedatives/anesthetics, stimulants, hallucinogens, antiepileptics) and are well-suited to various high-throughput applications (due to their high fecundity, rapid external development, transparency, fast drug intake, and robust behavioral and physiological phenotypes in both larval and adult fish). Finally, zebrafish emerge as an excellent model for neurogenetic analyses, as they have 25 pairs of chromosomes containing 26,000 protein-coding genes, with the overall genetic homology to mammals and humans around 75 %, and nearly 85 % of shared genes known to be associated with human disease. Collectively, this calls for a wider use of zebrafish models as a powerful promising model organism for neuroscience and drug discovery research.This study was supported by the Russian Science Foundation RSF grant 19‐15‐00053

Naloxone Prolongs Abdominal Constriction Writhing-Like Behavior in a Zebrafish-Based Pain Model

The ability to detect noxious stimuli is essential to survival. However, pathological pain is maladaptive and severely debilitating. Endogenous and exogenous opioids modulate pain responses via opioid receptors, reducing pain sensibility. Due to the high genetic and physiological similarities to rodents and humans, the zebrafish is a valuable tool to assess pain responses and the underlying mechanisms involved in nociception. Although morphine attenuates pain-like responses of zebrafish, there are no data showing if the antagonism of opioid receptors prolongs pain duration in the absence of an exogenous opioid. Here, we investigated whether a common opioid antagonist naloxone affects the abdominal constriction writhing-like response, recently characterized as a zebrafish-based pain behavior. Animals were injected intraperitoneally with acetic acid (5.0%), naloxone (1.25 mg/kg; 2.5 mg/kg; 5.0 mg/kg) or acetic acid with naloxone to investigate the changes in their body curvature for 1 h. Acetic acid elicited a robust pain-like response in zebrafish, as assessed by aberrant abdominal body curvature, while no effects were observed following PBS injection. Although naloxone alone did not alter the frequency and duration of this behavior, it dose-dependently prolonged acetic acid-induced abdominal curvature response. Besides reinforcing the use of the abdominal writhing-like phenotype as a behavioral endpoint to measure acute pain responses in zebrafish models, our novel data suggest a putative role of endogenous opioids in modulating the recovery from pain stimulation in zebrafish. © 2019 Elsevier B.V.We recognize the financial support and fellowships from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) . F.V.C. was recipient of CAPES fellowship. J.C. and F.V.S. receive the CNPq fellowship. D.B.R. is a recipient of CNPq research productivity grant ( 305051/2018-0 ) and his work is also supported by the PROEX/CAPES (process number 23038.005848/2018-31) and PRONEM/FAPERGS (process number 16/2551-0000248-7) fellowship grants. A.V.K. is the Chair of the International Zebrafish Neuroscience Research Consortium (ZNRC). His research is supported by the Russian Science Foundation (RSF) grant 19-15-00053. All authors contributed to the preparation of the manuscript and approved its final version. The funders had no influence on the study design, collection, analysis, and interpretation of data, as well as on writing and submission of this manuscript

Using Zebrafish in Preclinical Drug Studies: Challenges and Opportunities

Scientific relevance. Since fiscal and regulatory constraints substantially limit bioscreening in rodent models, a wider implementation of additional alternative models in preclinical studies of medicines is gaining momentum. These alternative models include aquatic vertebrates, such as zebrafish (Danio rerio).Aim. The study aimed to examine zebrafish models in terms of their performance in preclinical studies, their current uses, the challenges and opportunities in the field, and strategic directions for the development of preclinical testing in zebrafish.Discussion. Here, the authors summarise the key zebrafish tests that are currently used to assess a wide range of small molecules for their general and endocrine toxicity and effects on the survival of embryos and larvae. The review discusses the strengths and weaknesses of zebrafish models for preclinical testing of neurotropic agents. Additionally, the authors overview various methodological approaches to improving zebrafish toxicity testing. Overall, the use of zebrafish models is gradually becoming internationally established for laboratory testing of small molecules.Conclusions. A wider implementation of zebrafish models in pharmaceutical research and preclinical testing as an additional alternative to rodents, particularly in Russia, may significantly accelerate the development of novel medicinal products and foster a more comprehensive and adequate assessment of the biological risks associated with chemical substances

Zebrafish models in neuropsychopharmacology and CNS drug discovery

Despite the high prevalence of neuropsychiatric disorders, their aetiology and molecular mechanisms remain poorly understood. The zebrafish (Danio rerio) is increasingly utilized as a powerful animal model in neuropharmacology research and in vivo drug screening. Collectively, this makes zebrafish a useful tool for drug discovery and the identification of disordered molecular pathways. Here, we discuss zebrafish models of selected human neuropsychiatric disorders and drug-induced phenotypes. As well as covering a broad range of brain disorders (from anxiety and psychoses to neurodegeneration), we also summarize recent developments in zebrafish genetics and small molecule screening, which markedly enhance the disease modelling and the discovery of novel drug targets. © 2017 The British Pharmacological SocietyThe study was coordinated through the International Zebrafish Neuroscience Research Consortium (ZNRC), and this collaboration was funded by St. Petersburg State University, Ural Federal University and Guangdong Ocean University. A.V.K. is the Chair of ZNRC, and his research is supported by the Russian Foundation for Basic Research (RFBR) grant 16-04-00851

Zebrafish Models in NeuroPsychopharmacology and CNS Drug Discovery

Despite the high prevalence of neuropsychiatric disorders, their aetiology and molecular mechanisms remain poorly understood. The zebrafish (Danio rerio) is increasingly utilized as a powerful animal model in neuropharmacology research and in vivo drug screening. Collectively, this makes zebrafish a useful tool for drug discovery and the identification of disordered molecular pathways. Here, we discuss zebrafish models of selected human neuropsychiatric disorders and drug-induced phenotypes. As well as covering a broad range of brain disorders (from anxiety and psychoses to neurodegeneration), we also summarize recent developments in zebrafish genetics and small molecule screening, which markedly enhance the disease modelling and the discovery of novel drug targets

Age of the Donor Reduces the Ability of Human Adipose-Derived Stem Cells to Alleviate Symptoms in the Experimental Autoimmune Encephalomyelitis Mouse Model

There is a significant clinical need for effective therapies for primary progressive multiple sclerosis, which presents later in life (i.e., older than 50 years) and has symptoms that increase in severity without remission. With autologous mesenchymal stem cell therapy now in the early phases of clinical trials for all forms of multiple sclerosis (MS), it is necessary to determine whether autologous stem cells from older donors have therapeutic effectiveness. In this study, the therapeutic efficacy of human adipose-derived mesenchymal stem cells (ASCs) from older donors was directly compared with that of cells from younger donors for disease prevention. Mice were induced with chronic experimental autoimmune encephalomyelitis (EAE) using the myelin oligodendrocyte glycoprotein35-55 peptide and treated before disease onset with ASCs derived from younger ( \u3c 35 years) or older ( \u3e 60 years) donors. ASCs from older donors failed to ameliorate the neurodegeneration associated with EAE, and mice treated with older donor cells had increased central nervous system inflammation, demyelination, and splenocyte proliferation in vitro compared with the mice receiving cells from younger donors. Therefore, the results of this study demonstrated that donor age significantly affects the ability of human ASCs to provide neuroprotection, immunomodulation, and/or remyelination in EAE mice. The age-related therapeutic differences corroborate recent findings that biologic aging occurs in stem cells, and the differences are supported by evidence in this study that older ASCs, compared with younger donor cells, secrete less hepatocyte growth factor and other bioactive molecules when stimulated in vitro. These results highlight the need for evaluation of autologous ASCs derived from older patients when used as therapy for MS

\u27Vitamin D and cognition in older adults\u27: updated international recommendations.

BACKGROUND: Hypovitaminosis D, a condition that is highly prevalent in older adults aged 65 years and above, is associated with brain changes and dementia. Given the rapidly accumulating and complex contribution of the literature in the field of vitamin D and cognition, clear guidance is needed for researchers and clinicians. METHODS: International experts met at an invitational summit on \u27Vitamin D and Cognition in Older Adults\u27. Based on previous reports and expert opinion, the task force focused on key questions relating to the role of vitamin D in Alzheimer\u27s disease and related disorders. Each question was discussed and voted using a Delphi-like approach. RESULTS: The experts reached an agreement that hypovitaminosis D increases the risk of cognitive decline and dementia in older adults and may alter the clinical presentation as a consequence of related comorbidities; however, at present, vitamin D level should not be used as a diagnostic or prognostic biomarker of Alzheimer\u27s disease due to lack of specificity and insufficient evidence. This population should be screened for hypovitaminosis D because of its high prevalence and should receive supplementation, if necessary; but this advice was not specific to cognition. During the debate, the possibility of \u27critical periods\u27 during which vitamin D may have its greatest impact on the brain was addressed; whether hypovitaminosis D influences cognition actively through deleterious effects and/or passively by loss of neuroprotection was also considered. CONCLUSIONS: The international task force agreed on five overarching principles related to vitamin D and cognition in older adults. Several areas of uncertainty remain, and it will be necessary to revise the proposed recommendations as new findings become available

Comparative Analyses of Zebrafish Anxiety-Like Behavior Using Conflict-Based Novelty Tests

Modeling of stress and anxiety in adult zebrafish (Danio rerio) is increasingly utilized in neuroscience research and central nervous system (CNS) drug discovery. Representing the most commonly used zebrafish anxiety models, the novel tank test (NTT) focuses on zebrafish diving in response to potentially threatening stimuli, whereas the light-dark test (LDT) is based on fish scototaxis (innate preference for dark vs. bright areas). Here, we systematically evaluate the utility of these two tests, combining meta-analyses of published literature with comparative in vivo behavioral and whole-body endocrine (cortisol) testing. Overall, the NTT and LDT behaviors demonstrate a generally good cross-test correlation in vivo, whereas meta-analyses of published literature show that both tests have similar sensitivity to zebrafish anxiety-like states. Finally, NTT evokes higher levels of cortisol, likely representing a more stressful procedure than LDT. Collectively, our study reappraises NTT and LDT for studying anxiety-like states in zebrafish, and emphasizes their developing utility for neurobehavioral research. These findings can help optimize drug screening procedures by choosing more appropriate models for testing anxiolytic or anxiogenic drugs