Zebrafish as an emerging model for studying complex brain disorders

Abstract

The zebrafish (Danio rerio) is rapidly becoming a popular model organism in pharmacogenetics and neuropharmacology. Both larval and adult zebrafish are currently used to increase our understanding of brain function, dysfunction, and their genetic and pharmacological modulation. Here we review the developing utility of zebrafish in the analysis of complex brain disorders (including, e.g., depression, autism, psychoses, drug abuse, and cognitive deficits), also covering zebrafish applications towards the goal of modeling major human neuropsychiatric and drug-induced syndromes. We argue that zebrafish models of complex brain disorders and drug-induced conditions are a rapidly emerging critical field in translational neuroscience and pharmacology research.

Keywords: behavioral tests; brain disorders; translational research; zebrafish.

Figure 1. Zebrafish in laboratory research and natural environments

Panel (a) shows major zebrafish research centers established worldwide (red stars), including the National Institutes of Health (1), University of Oregon (2) and Washington University (3) in USA, and RIKEN Institute (4) in Japan. Inset – a typical rack housing hundreds of zebrafish in a research facility. (b) Typical habitat of zebrafish in the wild (shallow waters, e.g., rice fields) in various regions of South-East Asia (see ^, for details). (c) Larval and adult zebrafish (including several common color variants, also see Table 2 for zebrafish strain information). (d) The growing number of published zebrafish models (assessed in Pubmed in September 2013, using terms “zebrafish” and “behavior”).

Figure 2. The timeline of the developing utility of zebrafish models in neuroscience and neuropharmacology research

SSRI – selective serotonin reuptake inhibitors, ADHD – attention deficit/hyperactivity disorder, AD – Alzheimer’s disease, PD – Parkinson’s disease, AL – anxiolytic drugs, AE – antiepileptic drugs, SS – serotonin syndrome (serotonin toxicity), see Tables 1 and 3 for details (note that toxicology studies were not included here).

Figure 3. Comparison of zebrafish and mouse experimental models

Panel (a) shows the similarity of zebrafish and mouse brain morphology (OB – olfactory bulbs, TC – telencephalon, OT – optic tectum, Hb – habenula, CB – cerebellum, HB – hind brain, MD – medulla, SC – spinal cord, CR – cortex, Co – colliculi). Bottom inset: Golgi staining of zebrafish neurons (I) and their dendritic spines (II), showing similarity of zebrafish neuronal morphology to rodent neurons (photos by R. Mervis’ laboratory; Tampa, FL). Panel (b) shows how major zebrafish neurobehavioral tests of exploration, anxiety and locomotion parallel those traditionally used in rodents (adapted from ^{, , –}), combined with automated video-tracking using top-view (rodents) or top/side view cameras (zebrafish). Note predominantly 2D nature of rodent locomotion (X,Z plane) vs. 3D locomotion of zebrafish in X,Y,Z coordinates. Panel (c) shows typical anxiety-like behaviors observed in zebrafish in the novel tank diving test (including anxiety evoked by alarm substance acute 5-min exposure and reduced anxiety produced by a chronic 2-week 0.1 mg/l fluoxetine anxiolytic treatment, see Table 1 for explanation of behavioral signs of anxiety in zebrafish), an aquatic paradigm similar to rodent open field test (b). Note that alarm substance exposure test in zebrafish is similar to the cat odor rodent task. Panel (d) illustrates principles of high-throughput screens (HTS) using larval and adult zebrafish. Panels (e-h) show examples of zebrafish social and cognitive behavior tests (adapted from 66, 68, 136, . Panel (e) illustrates the shoaling test’s typical set up (top) and application of video-tracking tools to quantify zebrafish group behavior (bottom; photo from a collaborative project between Noldus IT, Netherlands and the Kalueff Laboratory). Panel (f) shows the aquatic social preference test (top) and its similarity to the mouse sociability test (bottom). Panel (g) shows behavioral similarity between zebrafish predator avoidance (e.g., Indian Leaf Fish, Nandus nandus) and the rat exposure mouse test. Panel (h) illustrates parallels between aquatic and rodent cognitive tasks, such as the T-maze test.

Figure 3. Comparison of zebrafish and mouse experimental models

Panel (a) shows the similarity of zebrafish and mouse brain morphology (OB – olfactory bulbs, TC – telencephalon, OT – optic tectum, Hb – habenula, CB – cerebellum, HB – hind brain, MD – medulla, SC – spinal cord, CR – cortex, Co – colliculi). Bottom inset: Golgi staining of zebrafish neurons (I) and their dendritic spines (II), showing similarity of zebrafish neuronal morphology to rodent neurons (photos by R. Mervis’ laboratory; Tampa, FL). Panel (b) shows how major zebrafish neurobehavioral tests of exploration, anxiety and locomotion parallel those traditionally used in rodents (adapted from ^{, , –}), combined with automated video-tracking using top-view (rodents) or top/side view cameras (zebrafish). Note predominantly 2D nature of rodent locomotion (X,Z plane) vs. 3D locomotion of zebrafish in X,Y,Z coordinates. Panel (c) shows typical anxiety-like behaviors observed in zebrafish in the novel tank diving test (including anxiety evoked by alarm substance acute 5-min exposure and reduced anxiety produced by a chronic 2-week 0.1 mg/l fluoxetine anxiolytic treatment, see Table 1 for explanation of behavioral signs of anxiety in zebrafish), an aquatic paradigm similar to rodent open field test (b). Note that alarm substance exposure test in zebrafish is similar to the cat odor rodent task. Panel (d) illustrates principles of high-throughput screens (HTS) using larval and adult zebrafish. Panels (e-h) show examples of zebrafish social and cognitive behavior tests (adapted from 66, 68, 136, . Panel (e) illustrates the shoaling test’s typical set up (top) and application of video-tracking tools to quantify zebrafish group behavior (bottom; photo from a collaborative project between Noldus IT, Netherlands and the Kalueff Laboratory). Panel (f) shows the aquatic social preference test (top) and its similarity to the mouse sociability test (bottom). Panel (g) shows behavioral similarity between zebrafish predator avoidance (e.g., Indian Leaf Fish, Nandus nandus) and the rat exposure mouse test. Panel (h) illustrates parallels between aquatic and rodent cognitive tasks, such as the T-maze test.

Figure 4. Comparative analysis of relative potencies of effective acute behavioral doses of selected psychotropic drugs in zebrafish and other species

Panel (a) shows glutamatergic antagonists dizocilpine (MK801), phencyclidine (PCP), ibogaine (Ibo), ketamine (Ket) and kynurenic acid (KYNA); ‘Normalized’ logarithmic dose range is 0.1–20 mg/L for zebrafish; 0.05–200 mg/kg for mice; 0.003–25 mg/kg for non-human primates; 0.01–15 mg/kg for humans. *Data for KYNA not available. Panel (b) shows zebrafish and human data for selected serotonergic drugs, including lysergic acid diethylamide (LSD), mescaline (Mes), psilocybin (Psi), and 3,4-methylenedioxymethamphetamine (MDMA); ‘Normalized’ logarithmic dose range is 0.1–120 mg/L for zebrafish and 0.0001–4 mg/kg for humans. Collectively, these data show similar ranking of drugs’ activity across various species, illustrating translational value of zebrafish models for screening clinically active neurotropic drugs.