Behavioral Analysis of Dopaminergic Activation in Zebrafish and Rats Reveals Similar Phenotypes

Abstract

Zebrafish is emerging as a complement to mammals in behavioral studies; however, there is a lack of comparative studies with rodents and humans to establish the zebrafish as a predictive translational model. Here we present a detailed phenotype evaluation of zebrafish larvae, measuring 300-3000 variables and analyzing them using multivariate analysis to identify the most important ones for further evaluations. The dopamine agonist apomorphine has previously been shown to have a complex U-shaped dose-response relationship in the variable distance traveled. In this study, we focused on breaking down distance traveled into more detailed behavioral phenotypes for both zebrafish and rats and identified in the multivariate analysis low and high dose phenotypes with characteristic behavioral features. Further analysis of single parameters also identified an increased activity at the lowest concentration indicative of a U-shaped dose-response. Apomorphine increased the distance of each swim movement (bout) at both high and low doses, but the underlying behavior of this increase is different; at high dose, both bout duration and frequency increased whereas bout max speed was higher at low dose. Larvae also displayed differences in place preference. The low dose phenotype spent more time in the center, indicative of an anxiolytic effect, while the high-dose phenotype had a wall preference. These dose-dependent effects corroborated findings in a parallel rat study and previous observations in humans. The translational value of pharmacological zebrafish studies was further evaluated by comparing the amino acid sequence of the dopamine receptors (D1-D4), between zebrafish, rats and humans. Humans and zebrafish share 100% of the amino acids in the binding site for D1 and D3 whereas D2 and D4 receptors share 85-95%. Molecular modeling of dopamine D2 and D4 receptors indicated that nonconserved amino acids have limited influence on important ligand-receptor interactions.

Action sequencing in the spontaneous swimming behavior of zebrafish larvae - implications for drug development

“…For example, the number of bouts displayed per unit time decreased throughout the experiments, except for high dose apomorphine which showed a more complex biphasic pattern (as previously reported by e.g. refs 32 and 35; Fig. 5A–D).…”

“…All experiments were repeated either two or three times in different groups of animals resulting in a total of 24 or 36 larvae in each treatment group. In the case of apomorphine two different dose regiments were explored based on the previously reported complex dose-response patterns 32 . For MK-801, slightly older larvae were used (15 dpf) since contradictory responses have previously been reported for this drug in younger animals 33, 34 .…”

“…Furthermore, it is interesting to note that if the complex sequencing of actions here discovered in zebrafish larvae reflects a shared functional role of the basal ganglia in vertebrates (cf. refs 32, 43, 44) this could make fish larvae a relevant model system for a whole range of disease conditions, including for example Parkinson’s disease and obsessive compulsive disorder. It could also pave the way for new ways to study genetic influences on behavior since zebrafish is a very widely used genetic model system.…”

Domperidone upregulates dopamine receptor expression and stimulates locomotor activity in larval zebrafish (Danio rerio)

“…Where the specific behavior of ZF to light‐dark intervals is more unique, a number of pharmacological studies have detailed the responses of ZF to DA receptor agonists and antagonists. Apomorphine, a DA agonist, is reported to have a biphasic impact on distance traveled in 10 dpf ZF at high doses (50 μM), with significant reductions in distance traveled from 0 to 5 minutes postexposure and significant increases after 25 to 35 minutes vs the control . Acute application of 5 μM L741,626, a D 2 ‐specific receptor antagonist, increased the occurrence of swimming episodes in 72 hpf ZF .…”

“…Apomorphine, a DA agonist, is reported to have a biphasic impact on distance traveled in 10 dpf ZF at high doses (50 μM), with significant reductions in distance traveled from 0 to 5 minutes postexposure and significant increases after 25 to 35 minutes vs the control. 51 Acute application of 5 μM L741,626, a D 2 -specific receptor antagonist, increased the occurrence of swimming episodes in 72 hpf ZF. 52 Conversely, adult ZF treated with 0.27 μM amisulpride, a D 2/3 receptor antagonist, moved less than fish treated with 2.7 μM amisulpride.…”