Modeling anxiety using adult zebrafish: a conceptual review

Abstract

Zebrafish (Danio rerio) are rapidly emerging as a useful animal model in neurobehavioral research. Mounting evidence shows the suitability of zebrafish to model various aspects of anxiety-related states. Here, we evaluate established and novel approaches to uncover the molecular substrates, genetic pathways and neural circuits of anxiety using adult zebrafish. Experimental approaches to modeling anxiety in zebrafish include novelty-based paradigms, pharmacological and genetic manipulations, as well as innovative video-tracking, 3D-reconstructions, bioinformatics-based searchable databases and omics-based tools. Complementing traditional rodent models of anxiety, we provide a conceptual framework for the wider application of zebrafish and other aquatic models in anxiety research. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Figure 1

Effects of tranylcypromine (TCP) (300–400 μg/L) exposure on adult wild type (short-fin) zebrafish behavior in the 6 min novel tank test. TCP was administered for 30 min followed by testing 1 week later. A one-way ANOVA test (factor: dose) revealed that the drug significantly affects the number of erratic movements (F_{(2, 41)} = 5.699, P < 0.05) in adult wild type (short-fin) zebrafish. Data are presented as mean ± SEM (n = 14 per group), *P<0.05 vs. control; post-hoc Tukey test for significant ANOVA data.

Figure 2

Effects of repeated lysergic acid diethylamide (LSD, 100 μg/L) exposure on adult wild type (short-fin) zebrafish behavior in the 6 min novel tank test. Zebrafish were exposed to LSD twice a day for one week. Wilcoxon U-test revealed that the drug significantly affects the time spent in the top in adult wild type (short-fin) zebrafish. Data are presented as mean ± SEM (n = 14 per group), ***P<0.005 vs. control, U-test.

Figure 3

Effects of acute 20-min dizocilpine (MK-801, 1–10 mg/L) exposure on adult wild type (short-fin) zebrafish behavior in the 6 min novel tank test. A one-way ANOVA test (factor: dose) revealed that the drug significantly affects the latency to enter the top (F_{(3, 55)} = 9.315, P < 0.005), time spent in the top (F_{(3, 55)} = 20.834, P < 0.005), number of erratic movement (F_{(3, 55)} = 4.563, P < 0.005), and number of freezing bouts (F_{(3, 55)} = 8.255, P < 0.005) in adult wild type (short-fin) zebrafish. Data are presented as mean ± SEM (n = 14 per group), *P<0.05, **P < 0.01, ***P < 0.005 vs. control; post-hoc Tukey test for significant ANOVA data.

Figure 4

Behavioral effects of the predator avoidance in adult wild type (short-fin) zebrafish in the two-compartment choice test. Zebrafish were placed in the center of the tank and the exposed to a predator (placed in an adjacent arm) for 6 min. The number or entries to, and the time spent in, the predator vs. non-predator containing arms was assessed. (A) In this experiment, zebrafish were exposed to two different predators simultaneously, the Indian leaf fish (ILF) and African leaf fish (ALF), with each placed in separate, opposite arms of the tank. Zebrafish generally exhibit stronger avoidance toward the open center arm and the ILF (indigenous to their natural environment in the wild) compared to the ALF. (B) In this experiment, zebrafish were exposed to either the ILF or ALF on alternating trials, during which the single predator was placed into one arm of the test apparatus. The number of arm entries and duration is significantly affected by ILF vs. ALF predator exposure. Data are presented as mean ± SEM (n = 15 per group), *P<0.05, **P < 0.005, #P = 0.05–0.09 vs. control, U-test