title: Exposure to D2-like dopamine receptor agonists inhibits swimming in Daphnia magna.
abstract: Daphnia are freshwater crustaceans that have been used for decades in ecotoxicology research. Despite the important role that Daphnia have played in environmental toxicology studies, very little is known about the neurobiology of Daphnia. Although many studies have investigated the swimming movements of these "water fleas", few studies have examined the underlying neurochemical basis for these movements. To characterize the locomotor effect of drugs in Daphnia, a two-dimensional video imaging tool was developed and animal tracking was performed with freely available software, CTRAX. Due to the central role that dopamine plays in the movement of animals, we sought to determine the role of dopamine receptor signaling in Daphnia movement by characterizing the effect of ten drugs that are agonists or antagonists of dopamine receptors. At 1, 2, and 6h of treatment with a 10μM drug, several dopamine receptor agonists with documented effects on the D2-like class of receptors decreased the movement. Further, we determined behavioral inhibition values (IC50) at 1h of treatment for (1R,3S)-1-(aminomethyl)-3-phenyl-3,4-dihydro-1H-isochromene-5,6-diol (A68930) to be 1.4μM and for bromocriptine to be 6.6μM. This study describes a new method to study Daphnia swimming and establishes this organism as a useful model for studies of dopaminergic signaling. Specifically, this study shows that a dopamine receptor signaling pathway, mediated by putative D2-like receptors, is involved in the control of Daphnia swimming behavior. Due to its ease of use and its rich motor program we propose that Daphnia should be considered for future studies of dopamine neuron toxicity and protection.
authors: Department of Biology, Augsburg College, 2211 Riverside Ave S, Minneapolis, MN 55454, United States. Electronic address: ebarrozo@ufl.edu.
authors: Enrico R
authors: ER
authors: Barrozo
authors: Department of Biology, Augsburg College, 2211 Riverside Ave S, Minneapolis, MN 55454, United States. Electronic address: david.fowler@alumni.augsburg.edu.
authors: David A
authors: DA
authors: Fowler
authors: Department of Biology, Augsburg College, 2211 Riverside Ave S, Minneapolis, MN 55454, United States. Electronic address: beckmanm@augsburg.edu.
authors: Matthew L
authors: ML
authors: Beckman
mesh_terms: D000818:Animals; D003621:Daphnia; D018491:Dopamine Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000819:agonists* / Q000502:physiology; D013550:Swimming / Q000502:physiology
chemical_list: D018491:Dopamine Agonists; D017448:Receptors, Dopamine D2
keywords: Behavior; CTRAX; Daphnia; Dopamine; Dopamine receptor; Dose–response; Imaging; Swimming; Tracking