The neuropeptide Pth2 modulates social behavior and anxiety in zebrafish

Effects of sodium arsenite exposure on behavior, ultrastructure and gene expression of brain in adult zebrafish (Danio rerio)

Arsenic, a common metal-like substance, has been demonstrated to pose potential health hazards and induce behavioral changes in humans and rodents. However, the chronic neurotoxic effects of arsenic on aquatic animals are still not fully understood. This study aimed to investigate the effects of arsenic exposure on adult zebrafish by subjecting 3-month-old zebrafish to three different sodium arsenite water concentrations: 0 μg/L (control group), 50 μg/L, and 500 μg/L, over a period of 30 days. To assess the risk associated with arsenic exposure in the aquatic environment, behavior analysis, transmission electron microscopy techniques, and quantitative real-time PCR were employed. The behavior of adult zebrafish was evaluated using six distinct tests: the mirror biting test, shoaling test, novel tank test, social preference test, social recognition test, and T maze. Following the behavioral tests, the brains of zebrafish were dissected and collected for ultrastructural examination and gene expression analysis. The results revealed that sodium arsenite exposure led to a significant reduction in aggression, cohesion, social ability, social cognition ability, learning, and memory capacity of zebrafish. Furthermore, ultrastructure and genes regulating behavior in the zebrafish brain were adversely affected by sodium arsenite exposure.

Multisensory navigational strategies of hatchling fish for dispersal

Animals influence how they disperse in the environment by sensing local cues and adapting how they move. However, controlling dispersal can present a particular challenge early in life when animals tend to be more limited in their capacities to sense and move. To what extent and by what mechanisms can newly hatched fish control how they disperse? Here, we reveal hatchling sensorimotor mechanisms for controlling dispersal by combining swim tracking and precise sensory manipulations of a model species, zebrafish. In controlled laboratory experiments, if we physically constrained hatchlings or blocked sensations of motion through vision and the lateral line, hatchlings responded by elevating their buoyancy and passively moving with faster surface currents. Complementarily, in stagnant water, hatchlings covered more ground using hyperstable swimming, strongly orienting based on graviception. Using experimentally calibrated hydrodynamic simulations, we show that these hatchling behaviors nearly tripled diffusivity and made dispersal robust to local conditions, suggesting this multisensory strategy may provide important advantages for early life in a variable environment.

Vasotocin expression is associated with social preference development of the medaka fish

The neurohypophysial peptide arginine vasotocin (VT) and its mammalian ortholog, arginine vasopressin, function in physiological and behavioral events. These functions have been identified in neuroendocrinological studies using adult animals; however, there is little information on whether VT is associated with social behavior development in fish. Here, we examined social preference in medaka fish of various ages and investigated how VT expression changes during development. The 1-, 2-, 4-, and 8-week post-hatching (wph) larvae, juveniles, and 5-month-old adults were individually introduced to the grouped fish of each age group, and the social preference index (SPI) was compared among ages based on the time spent in the interaction zone near the grouped fish in a test tank. The SPI was significantly higher in the 4-wph larvae, 8-wph juveniles, and adult fish than in the 1- and 2-wph larvae. VT expression increased with age from 1 to 4 wph. Similarly, the expression was high in 4-wph, 8-wph, and adult fish. Furthermore, it was also found that the SPI and the VT expression decreased in the socially isolated larva during the 4 weeks after hatching compared to the levels in the grouped 4-wph larvae. These findings suggest that social preference develops with age and that conspecifics are necessary for social development in medaka larvae. Furthermore, our results suggest that VT is associated with the development of social preferences in medaka.

angptl4 gene expression as a marker of adaptive homeostatic response to social isolation across the lifespan in zebrafish

Social isolation has detrimental health effects, but the underlying mechanisms are unclear. Here, we investigated the impact of 2 weeks of isolation on behavior and gene expression in the central nervous system at different life stages of zebrafish. Results showed that socially deprived young adult zebrafish experienced increased anxiety, accompanied by changes in gene expression. Most gene expression patterns returned to normal within 24 hours of reintroduction to a social environment, except angptl4, which was upregulated after reintroduction, suggesting an adaptive mechanism. Similarly, aging zebrafish displayed heightened anxiety and increased central nervous system expression of angptl4 during isolation, but effects were reversed upon reintroduction to a social group. The findings imply that angptl4 plays a homeostatic role in response to social isolation, which varies across the lifespan. The study emphasizes the importance of social interactions for psychological well-being and highlights the negative consequences of isolation, especially in older individuals. Further research may unravel how social isolation affects angptl4 expression and its developmental and aging effects.

Isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate plays an anti-hypoxic role through regulating neuroactive ligand-receptor interaction signaling pathway in larval zebrafish

Isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate (IDHP) is the core active substance of salvia miltiorrhiza in disease treatment. The significance of our work lies in evaluating the ameliorating effects of IDHP on hypoxia-induced injury and investigating its mechanisms. We examined the morphology, dopamine neurons (DANs), cerebral vessels, and behavior of zebrafish larvae administrated by IDHP/VHC after hypoxia-induction. We next sought to explore its anti-hypoxic mechanisms via transcriptome analysis and qPCR experiments. The results indicated that hypoxia-induced injuries, including decreased length of DANs, number of cereal vessels, total swimming distance, and average swimming speed, were all alleviated by IDHP. Furthermore, transcriptome analysis provided a sign that IDHP most likely played the anti-hypoxic role through the neuroactive ligand-receptor interaction (NLRI) signaling pathway. Consistently, expression of related genes, such as f2rl1.1, p2ry10, npy1r, ptger2b, ptger2b, pth2rb, and nmur1a, was downregulated by hypoxia induction and recovered after IDHP administration. Therefore, we speculated that, via regulating NLRI, IDHP reduced inflammation, promoted angiogenesis, modulated blood pressure and flow, and inhibited cell apoptosis, and eventually played an anti-hypoxic role.

Changes in aggression and locomotor behaviors in response to zinc is accompanied by brain cell heterogeneity and metabolic and circadian dysregulation of the brain-liver axis

Zinc is an essential nutrient for life, but over-accumulation can result in toxicity. Anthropogenic activities can increase zinc concentrations in aquatic environments (e.g., to ∼0.46-1.00 mg/L), which are above the safe level of 0.1 mg/L. We investigated the behavior and physiology of zebrafish (Danio rerio) in response to environment-related exposure to zinc chloride at 0.0 (Ctrl), 1.0 (ZnCl₂-low) and 1.5 (ZnCl₂-high) mg/L for 6 weeks (the zinc conversion ratio of zinc chloride is ∼0.48 and the nominal (measured) values were: Ctrl, 0 (∼0.01); ZnCl₂-low, 0.48 (∼0.51); ZnCl₂-high, 0.72 (∼0.69) mg/L). Low-zinc exposure resulted in significantly increased locomotion and fast moving behaviors, while high-zinc exposure resulted in significantly increased aggression and freezing frequency. Single cell RNA-seq of neurons, astrocytes, and oligodendrocytes of the brain revealed expression of genes related to ion transport, neuron generation, and immunomodulation that were heterogeneously regulated by zinc exposure. Astrocyte-induced central nervous system inflammation potentially integrated neurotoxicity and behavior. Integrated analyses of brain and hepatic transcriptional signatures showed that genes (and pathways) dysregulated by zinc were associated with sensory functions, circadian rhythm, glucose and lipid metabolism, and amyloid β-protein clearance. Our results showed that environment-related zinc contamination can be heterogeneously toxic to brain cells and can disturb coordination of brain-liver physiology. This may disrupt neurobehavior and cause a neurodegeneration-like syndrome in adult zebrafish.

A Critical Review of Zebrafish Neurological Disease Models-2. Application: Functional and Neuroanatomical Phenotyping Strategies and Chemical Screens

Extensive phylogenetic conservation of molecular pathways and neuroanatomical structures, associated with efficient methods for genetic modification, have been exploited increasingly to generate zebrafish models of human disease. A range of powerful approaches can be deployed to analyze these models with the ultimate goal of elucidating pathogenic mechanisms and accelerating efforts to find effective treatments. Unbiased neurobehavioral assays can provide readouts that parallel clinical abnormalities found in patients, although some of the most useful assays quantify responses that are not routinely evaluated clinically, and differences between zebrafish and human brains preclude expression of the full range of neurobehavioral abnormalities seen in disease. Imaging approaches that use fluorescent reporters and standardized brain atlases coupled with quantitative measurements of brain structure offer an unbiased means to link experimental manipulations to changes in neural architecture. Together, quantitative structural and functional analyses allow dissection of the cellular and physiological basis underlying neurological phenotypes. These approaches can be used as outputs in chemical modifier screens, which provide a major opportunity to exploit zebrafish models to identify small molecule modulators of pathophysiology that may be informative for understanding disease mechanisms and possible therapeutic approaches.

Quantity as a Fish Views It: Behavior and Neurobiology

An ability to estimate quantities, such as the number of conspecifics or the size of a predator, has been reported in vertebrates. Fish, in particular zebrafish, may be instrumental in advancing the understanding of magnitude cognition. We review here the behavioral studies that have described the ecological relevance of quantity estimation in fish and the current status of the research aimed at investigating the neurobiological bases of these abilities. By combining behavioral methods with molecular genetics and calcium imaging, the involvement of the retina and the optic tectum has been documented for the estimation of continuous quantities in the larval and adult zebrafish brain, and the contributions of the thalamus and the dorsal-central pallium for discrete magnitude estimation in the adult zebrafish brain. Evidence for basic circuitry can now be complemented and extended to research that make use of transgenic lines to deepen our understanding of quantity cognition at genetic and molecular levels.