Differential effects of acute administration of SCH-23390, a D₁ receptor antagonist, and of ethanol on swimming activity, anxiety-related responses, and neurochemistry of zebrafish

Acute Administration of Ethanol and of a D1-Receptor Antagonist Affects the Behavior and Neurochemistry of Adult Zebrafish

Alcohol abuse represents major societal problems, an unmet medical need resulting from our incomplete understanding of the mechanisms underlying alcohol’s actions in the brain. To uncover these mechanisms, animal models have been proposed. Here, we explore the effects of acute alcohol administration in zebrafish, a promising animal model in alcohol research. One mechanism via which alcohol may influence behavior is the dopaminergic neurotransmitter system. As a proof-of-concept analysis, we study how D1 dopamine-receptor antagonism may alter the effects of acute alcohol on the behavior of adult zebrafish and on whole brain levels of neurochemicals. We conduct these analyses using a quasi-inbred strain, AB, and a genetically heterogeneous population SFWT. Our results uncover significant alcohol x D1-R antagonist interaction and main effects of these factors in shoaling, but only additive effects of these factors in measures of exploratory behavior. We also find interacting and main effects of alcohol and the D1-R antagonist on dopamine and DOPAC levels, but only alcohol effects on serotonin. We also uncover several strain dependent effects. These results demonstrate that acute alcohol may act through dopaminergic mechanisms for some but not all behavioral phenotypes, a novel discovery, and also suggest that strain differences may, in the future, help us identify molecular mechanisms underlying acute alcohol effects.

Dopamine Homeostasis Imbalance and Dopamine Receptors-Mediated AC/cAMP/PKA Pathway Activation are Involved in Aconitine-Induced Neurological Impairment in Zebrafish and SH-SY5Y Cells

Aconitine is one of the main bioactive and toxic ingredients of Aconitum species. Increasingly, aconitine has been reported to induce neurotoxicity. However, whether aconitine has effects on the dopaminergic nervous system remains unclear. In this study, zebrafish embryos at 6-days postfertilization were exposed to aconitine at doses of 0.5, 1, and 2 μM for 24 h, and SH-SY5Y cells were treated with 50, 100, and 200 μM of aconitine for 24 h. Results demonstrated that aconitine treatment induced deformities and enhanced the swimming behavior of zebrafish larvaes. Aconitine exposure suppressed cell proliferation and increased the number of reactive oxygen species and apoptosis in zebrafish larvaes and SH-SY5Y cells. Aconitine altered the levels of dopamine and its metabolites by regulating the expression of genes and proteins related to dopamine synthesis, storage, degradation, and reuptake in vivo and in vitro. Moreover, aconitine activated the AC/cAMP/PKA pathway by activating the dopamine D1 receptor (D1R) and inhibiting the dopamine D2 receptor (D2R) to disturb intracellular calcium homeostasis, eventually leading to the damage of nerve cells. Furthermore, the D1R antagonist SCH23390 and D2R agonist sumanirole pretreatment effectively attenuated the excitatory state of larvaes. Sumanirole and PKA antagonist H-89 pretreatment effectively decreased intracellular Ca²⁺ accumulation induced by aconitine in vivo. SCH23390 and sumanirole also reduced aconitine-induced cytotoxicity by inhibiting the AC/cAMP/PKA pathway in vitro. These results suggested that dopamine homeostasis imbalance and dopamine receptors (DRs)-mediated AC/cAMP/PKA pathway activation might be vital mechanisms underlying aconitine-induced neurological injury.

Acute ethanol induces behavioral changes and alters c-fos expression in specific brain regions, including the mammillary body, in zebrafish

Ethanol is one of the most commonly abused substances in the world, and ethanol abuse and dependence disorders represent major societal problems. However, appropriate treatment is lacking as we still do not fully understand the molecular bases of these disorders. The zebrafish is one of the model organisms utilized for studying such mechanisms. In this study, we examined the effects of acute ethanol administration on the behavior of zebrafish, and we also analyzed correlated gene expression changes using whole-mount in situ hybridization focusing on a number of genes associated with different neurotransmitter systems, stress response, and neuronal activity. We found ethanol treatment to result in hyperactivity and reduced shoal cohesion compared to control. Analysis of c-fos expression demonstrated altered activity patterns in certain brain regions, including intense activation of the mammillary body in zebrafish with acute ethanol treatment. We also found reduced level of gad1b expression in the cerebellum of ethanol treated fish compared to control. However, we could not detect significant changes in the expression level of other genes, including vglut2b, th, crh, hdc, avp, pomc, and galn in ethanol treated fish compared controls. Our results suggest that zebrafish is a promising animal model for the study of mechanisms underlying alcohol induced behavioral changes and alcohol related human disorders.

Formulation optimization, anesthetic activity, skin permeation, and transportation pathway of Alpinia galanga oil SNEDDS in zebrafish (Danio rerio)

Alpinia galanga oil (AGO) has an anesthetic activity but its water insoluble property limits its clinical applications. The aim of the present study was to develop a self-nanoemulsifying drug delivery system of AGO (SNEDDS-AGO) to avoid the use of organic solvent and investigate AGO transportation pathway and anesthetic activity. Three optimized formulations from a contour plots of droplet size; SNEDDS-AGO-1, SNEDDS-AGO-2, and SNEDDS-AGO-3, composed of AGO, Miglyol 812, Cremophor RH 40, Capmul MCM EP, and ethanol at the ratios of 40:10:35:10:5, 40:20:15:20:5, and 60:10:15:10:5, respectively were selected as they possessed different droplet size of 62 ± 0.5, 107 ± 2.8, and 207 ± 4.3 nm, respectively. It was found that the droplet size played an important role in fish anesthesia. SNEDDS-AGO-3 showed the longest anesthetic induction time (270 sec) (p < 0.03). Transportation pathway and skin permeation of SNEDDS-AGO-2 were investigated using nile red labelled AGO and detected by fluorescence microscope. AGO was found mostly in brain, gills, and skin suggesting that the transportation pathway of AGO in zebrafish is passing through the gills and skin to the brain. SNEDDS-AGO formulations showed significantly higher permeation through the skin than AGO ethanolic solution. In conclusion, SNEDDS is a promising delivery system of AGO.

Understanding the neurobiological effects of drug abuse: Lessons from zebrafish models

Drug abuse and brain disorders related to drug comsumption are public health problems with harmful individual and social consequences. The identification of therapeutic targets and precise pharmacological treatments to these neuropsychiatric conditions associated with drug abuse are urgently needed. Understanding the link between neurobiological mechanisms and behavior is a key aspect of elucidating drug abuse-related targets. Due to various molecular, biochemical, pharmacological, and physiological features, the zebrafish (Danio rerio) has been considered a suitable vertebrate for modeling complex processes involved in drug abuse responses. In this review, we discuss how the zebrafish has been successfully used for modeling neurobehavioral phenotypes related to drug abuse and review the effects of opioids, cannabinoids, alcohol, nicotine, and psychedelic drugs on the central nervous system (CNS). Moreover, we summarize recent advances in zebrafish-based studies and outline potential advantages and limitations of the existing zebrafish models to explore the neurochemical bases of drug abuse and addiction. Finally, we discuss how the use of zebrafish models may present fruitful approaches to provide valuable clinically translatable data.

Effect of triadimefon and its metabolite on adult amphibians Xenopus laevis

The decrease in the population of amphibians all over the world has raised concerns. Adult X. laevis frogs were exposed to 0, 1 and 10 mg/L triadimefon and triadimenol. After 14 or 28 days exposure, we collected male and female specimens to study swimming activity, lactic dehydrogenase (LDH) and antioxidant enzyme activity in blood samples, histopathology of liver and thyroid tissue, thyroid hormone levels and thyroid hormone-related gene expression levels in brains. Our results showed that triadimefon and triadimenol could affect the swimming activity of frogs and that this was distinct at different levels of triadimenol. Moreover, triadimefon and triadimenol exposure produced a greater effect on superoxide dismutase (SOD) in females than in males, which was reverse to the finding for glutathione S-transferase (GST) and catalase (CAT). After 28 days exposure, triadimefon produced more toxic effects on the liver than observed for triadimenol. Besides this, triadimefon and triadimenol exposure exerted a greater effect on liver histology and thyroid hormone levels in male frogs than in the females. Our results also found that the expression of genes related to thyroid hormone in brains depended on the exposure level and time, as well as the sex of the treated individual. This study shed light on the relationships between the toxicity of metabolite products and their parent compounds and provided further understanding of the risk of pesticide use on amphibians.

Dose dependent behavioral effects of acute alcohol administration in zebrafish fry

The zebrafish is becoming increasingly utilized in behavioral neuroscience as it appears to strike a good compromise between practical simplicity and system complexity. Particularly in alcohol (ethanol) research, the zebrafish has been employed as a translationally relevant model organism. However, the majority of studies investigating the effects of alcohol on brain function and behavior has used adult zebrafish. In the current study, we utilize 6-8 post-fertilization day old larval zebrafish (fry) to investigate the effects of a 40 min-long, acute, immersion into the alcohol bath. We measure the behavioral responses of the fry during the immersion session in relatively large arenas, the petri dish, instead of the often employed 96 well plate, and report on significant modification of behavior induced by alcohol. For example, we found the intermediate dose of alcohol (0.5%, vol/vol) to exert a stimulant effect manifesting as slight elevation of swim speed, robust increase of turning, temporal variability of swim speed and turning, and diminished frequency of staying immobile. We also found the high dose of 1% alcohol to elicit an opposite response, a sedative effect. This biphasic dose response of alcohol mimics what has been found in mammals, including humans, and thus we conclude that a few day-old zebrafish fry may be a cost effective and efficient tool with which one can screen for small molecules or mutations with alcohol-effect modifying properties.

Pharmacological (ethanol) and mutation (sam2 KO) induced impairment of novelty preference in zebrafish quantified using a new three-chamber social choice task

Social behavior is a fundamental aspect of our own species, a feature without which our society would not function. There are numerous human brain disorders associated with abnormal social behavior, among them are the autism spectrum disorders whose causal factors include a genetic component. Environmental factors, including drugs of abuse such as alcohol, also contribute to numerous abnormalities related to social behavior. Several such disorders have been modeled using laboratory animals. Perhaps one of the newest among them is the zebrafish. However, the paucity of standardized behavioral assays specifically developed for the zebrafish have hindered progress. Here, we present a newly developed zebrafish behavioral paradigm, the three-chamber social choice task. This task, which was adapted from a murine model, assesses sociality and social novelty preference in zebrafish in three phases: habituation, phase-I to evaluate sociality, and phase-II to quantify social novelty preference. Test fish are placed in the middle chamber, while conspecifics are introduced to the flanking chambers during phase-I and II. Both male and female zebrafish displayed sociality (preference for conspecifics) during phase-I and social novelty preference (preference for unfamiliar conspecifics) during phase-II. We found the paradigm to be able to detect both environmentally (alcohol) as well as genetically (targeted knock out of sam2) induced alterations of behavioral phenotypes. Although ethanol-treated fish displayed similar levels of sociality to those of control (not alcohol exposed) male and female zebrafish, they were found to exhibit significantly impaired social novelty preference, a finding compatible with altered motivational or perhaps mnemonic processes. Moreover, we found that knock out of sam2, previously shown to lead to emotional dysregulation, also disrupted social novelty preference, while leaving sociality relatively intact. We conclude that our novel behavioral paradigm is appropriate for the modeling and quantification of social behavior deficits in zebrafish.

Dopamine D1 and D2 receptor antagonism during development alters later behavior in zebrafish

This study sought to examine the long-term behavioral impacts of dopamine D₁ and D₂ receptor antagonism during development in zebrafish (Danio rerio). Zebrafish embryos of both the AB* and 5D strains were exposed via immersion to either the D₁ receptor antagonist SCH-23,390 or the D₂ receptor antagonist haloperidol, at either 0.5 or 1.5-μM, from 5 h post-fertilization to 5 days post-fertilization. Aquarium water served as a control. Fish were then either tested as larvae on day 6 post-fertilization on a light/dark locomotor assay, or were grown to adulthood and tested on a behavioral battery that included assays for novel environment exploration, startle habituation, social affiliation, and predator escape (AB* strain only). Overall, developmental exposure to dopamine D₁ and D₂ receptor antagonists caused clear effects in larval locomotor behavior, driving hyperactivity in dark phases and hypoactivity in light phases. Additionally, control fish from the two strains were significantly different from each other (p < 0.05) with the AB* fish being more active than SD during the dark periods of the test. In the adult behavioral battery, developmental exposure to 1.5-μM of the D₁ antagonist SCH-23390 significantly reduced activity (p < 0.05) in the predator escape assay. Despite the fact that embryonic exposure to D₁ and D₂ receptor antagonists caused clear behavioral alterations in larval activity there were much more subtle effects persisting into adulthood.

Pharmacological analysis of zebrafish lphn3.1 morphant larvae suggests that saturated dopaminergic signaling could underlie the ADHD-like locomotor hyperactivity

Polymorphisms in the gene coding for the adhesion G-protein coupled receptor LPHN3 are a risk factor for attention-deficit/hyperactivity disorder (ADHD). Transient down-regulation of latrophilin3.1 (lphn3.1), the zebrafish LPHN3 homologue, causes hyperactivity. Zebrafish injected with a lphn3.1-specific morpholino are hyperactive and display an impairment in dopaminergic neuron development. In the present study we used lphn3.1 morphants to further characterize the changes to dopaminergic signaling that trigger hyperactivity. We applied dopamine agonists (Apomorphine, Quinpirole, SKF-38393) and antagonists (Haloperidol, Eticlopride, SCH-23390) to Lphn3.1 morpholino-injected or control-injected animals. The percentage of change in locomotor activity was then determined at three different time periods (10-20 min, 30-40 min and 60-70 min). Our results show that drugs targeting dopamine receptors appear to elicit similar effects on locomotion in zebrafish larvae and mammals. In addition, we observed that lphn3.1 morphants have an overall hyposensitivity to dopamine agonists and antagonists compared to control fish. These results are compatible with a model whereby dopaminergic neurotransmission is saturated in lphn3.1 morphants.

Time-dependent interacting effects of caffeine, diazepam, and ethanol on zebrafish behaviour

Zebrafish have become a popular animal model for behavioural pharmacology due to their small size, rapid development, and amenability to high throughput behavioural drug screens. Furthermore, water-soluble compounds can be administered via immersion of the fish in the drug solution, which provides a non-invasive drug delivery method. Numerous studies have demonstrated stimulant effects of alcohol. Diazepam and caffeine, on the other hand have been found to have inhibitory effect on locomotor activity in zebrafish. However, the time-dependent changes induced by these psychoactive drugs are rarely reported, and potential drug interactions have not been examined in zebrafish, despite the translational relevance of this question. In the current study, we examine time- and dose-dependent changes in zebrafish following exposure to caffeine, diazepam, and ethanol quantifying four different behavioural parameters over a 30min recording session. We subsequently analyze potential drug-drug interactions by co-administering the three drugs in different combinations. Our time-course and dose-response analyses for each of the three drugs represent so far the most detailed studies available serving as a foundation for future psychopharmacology experiments with zebrafish. Furthermore, we report significant interactions between the three drugs corroborating findings obtained with rodent models as well as in humans, providing translational relevance for the zebrafish model.

Alcohol-induced behavioral changes in zebrafish: The role of dopamine D2-like receptors

RATIONALE

The dopaminergic system has been proposed to mediate alcohol-induced locomotor activity, yet the mechanisms underlying this behavioral response remain poorly understood.

OBJECTIVES

This study was conducted to investigate the role of dopamine D2-like receptors in mediating alcohol-induced behavioral responses.

METHODS

In experiment 1, we examined the effects of high concentrations (0, 2.5, 5, 10 μM) of haloperidol on motor responses. In experiment 2, we examined the effects of low concentrations (0, 0.625, 1.25, 2.5 μM) of haloperidol on anxiety-like behavioral responses using the novel tank test. In experiment 3, we examined the effect of pre-treating zebrafish with different concentrations of haloperidol (0, 0.625, 2.5 μM) and subsequently exposing them to 0 or 1 % alcohol.

RESULTS

In experiment 1, haloperidol induced an inverted U-shaped concentration-dependent increase in locomotor activity. In experiment 2, haloperidol (2.5 μM) reduced the absolute turn angle and freezing behavior in a new environment. In experiment 3, acute alcohol exposure significantly increased locomotor activity and decreased anxiety-like behavioral responses. Pre-treating zebrafish with the lower dose of haloperidol (0.625 μM) abolished the alcohol-induced locomotor activity, without altering anxiety-like behavioral responses. However, pre-treating with the higher dose of haloperidol (2.5 μM) abolished both alcohol-induced increase of locomotor activity and reduction of anxiety-like behavioral responses.

CONCLUSION

The results suggest alcohol-induced locomotor hyperactivity in zebrafish is mediated via activation of dopamine D2-like receptors, whereas anxiety-like behavioral responses may only be altered by a high haloperidol concentration, at which dose the drug may affect receptors other than D2-R.

Leveraging Large-scale Behavioral Profiling in Zebrafish to Explore Neuroactive Polypharmacology

Many psychiatric drugs modulate the nervous system through multitarget mechanisms. However, systematic identification of multitarget compounds has been difficult using traditional in vitro screening assays. New approaches to phenotypic profiling in zebrafish can help researchers identify novel compounds with complex polypharmacology. For example, large-scale behavior-based chemical screens can rapidly identify large numbers of structurally diverse and phenotype-related compounds. Once these compounds have been identified, a systems-level analysis of their structures may help to identify statistically enriched target pathways. Together, systematic behavioral profiling and multitarget predictions may help researchers identify new behavior-modifying pathways and CNS therapeutics.

Concentration, population, and context-dependent effects of AM251 in zebrafish

RATIONALE

The function of the cannabinoid type 1 receptor (CB1-R) is poorly understood in zebrafish, and numerous inconsistent effects have been reported on it in the literature.

OBJECTIVE

The objective of the present study is to determine whether differences in the reported effects of CB1-R antagonism on anxiety-like behavioural responses, dopaminergic and serotonergic responses are due to concentration, context-dependent and/or population (genotype-related) effects.

METHOD

Two genetically distinct populations of zebrafish (AB and short fin (SF)) were treated with different concentrations of AM251 (0, 0.1, 1mg/L), and behavioural responses were quantified under two different contexts: one, following habituation and two, subsequently in a novel environment. The levels of dopamine, serotonin and their metabolites 3,4-dihydroxyindole acetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) were quantified from whole-brain tissue.

RESULTS

We demonstrate that a 60-min exposure to AM251 (0, 0.1, 1mg/L) does not alter behavioural performance following habituation in either populations. However, when subsequently transferred to a novel environment, zebrafish that were pre-treated with the highest dose of AM251 (1mg/L) exhibited increased anxiety-like behavioural responses including elevated absolute turn angle, freezing and bottom dwelling. We found that exposure to the highest dose of AM251 (1mg/L) for 60min increased serotonin in fish of both populations tested. In contrast, exposure to 0.1mg/L AM251 decreased, whereas to 1mg/L AM251 increased dopamine, DOPAC and 5-HIAA in fish of both populations.

CONCLUSION

Our results demonstrate a genotype-independent effect of AM251 but imply that the inconsistent findings obtained after pharmacological blockade of CB1-Rs in zebrafish may be due to a combination of concentration- and environmental context-dependent effects.

Home tank water versus novel water differentially affect alcohol-induced locomotor activity and anxiety related behaviours in zebrafish

The zebrafish may be uniquely well suited for studying alcohol's mechanisms of action in vivo, since alcohol can be administered via immersion in a non-invasive manner. Despite the robust behavioural effects of alcohol administration in mammals, studies reporting the locomotor stimulant and anxiolytic effects of alcohol in zebrafish have been inconsistent. In the current study, we examined whether differences in the type of water used for alcohol exposure and behavioural testing contribute to these inconsistencies. To answer this question, we exposed zebrafish to either home water from their housing tanks or novel water from an isolated reservoir (i.e. water lacking zebrafish chemosensory and olfactory cues) with 0% or 1% v/v alcohol for 30 min, a 2 × 2 between subject experimental designs. Behavioural responses were quantified throughout the 30-minute exposure session via a video tracking system. Although control zebrafish exposed to home water and novel water were virtually indistinguishable in their behavioural responses, alcohol's effect on locomotor activity and anxiety-like behavioural responses were dependent on the type of water used for testing. Alcohol exposure in home tank water produced a mild anxiolytic and locomotor stimulant effect, whereas alcohol exposure in novel water produced an anxiogenic effect without altering locomotor activity. These results represent a dissociation between alcohol's effects on locomotor and anxiety related responses, and also illustrate how environmental factors, in this case familiarity with the water, may interact with such effects. In light of these findings, we urge researchers to explicitly state the type of water used.