Authors: Andrew Wengrovitz, Mansi Patel, Nader Ahmadeih, Christopher Souders II, Christopher Martyniuk
Faculty Mentor: Christopher Martyniuk
College: College of Veterinary Medicine
Ropinirole is a dopamine receptor agonist that is used in the treatment of Parkinson’s disease and Restless Leg Syndrome. The specific action of ropinirole is to activate D2 receptors, but it can also activate D3 and D4 receptor signaling. Zebrafish have been used to study the pharmacological stimulation and inhibition of dopamine receptors in relation to behavior in order to better understand the role of dopamine signaling in locomotion. In this study, 7-day old zebrafish larvae were exposed to ropinirole at concentrations of 1, 10 and 100 μM for 3 hours. Locomotor behavior was assessed following treatment with ropinirole using alternating periods of light and dark (photosensitization). Since dopamine is critical in cognition and motor movement, we hypothesized that an exposure to ropinirole at critical stages within the developmental zebrafish lifecycle would reduce activity in zebrafish larvae. After experimentation, we found that there was a significant dose response in each of the 3 dark intervals, with no differences between control and fish exposed to ropinirole in the light intervals. We are now examining the effects of ropinirole on the dopamine system of zebrafish at the molecular level. This study aims to associate molecular changes to activity responses in zebrafish.
This is a really cool idea! Why did you specifically use larval zebrafish?
Great question. Larval zebrafish were used for a couple of reasons- the first being that they are a model toxicological organism and share a similar genetic structure to humans. Thus, we can use the findings from researching these fish to make inferences about what would happen to humans. Additionally, zebrafish are fairly easy to breed and maintain. On any given day, these fish can give you well over 1000 embryos to work with for your project. Also, they are small and do not take up much space within a lab, which has some cost-effective benefits as well. It seems that within the field of environmental toxicology, many researchers are transitioning away from using mice/rats and starting to use these zebrafish.
I used larval fish because it eliminated some variables that I would otherwise have to account for. For my project, I raised the fish from embryos to 7 days post-fertilization, so I knew exactly what their life had entailed leading up to their exposure to Ropinirole. There were no questions of how old some of the fish were, what nutrients they had received, ets. Additionally, by day 7, these fish have mostly developed their complete organ systems, so prolonging the exposure any longer would only increase the chance of contaminating the experiment.
Hope that answers your question!
Hi, this is a very interesting project! I was wondering whether the 1 and 10 μM concentrations of Ropinirole had any effects on the zebrafish? Thank you!
Thanks for the question. Both the 1 and 10 μM concentrations had effects on the zebrafish. These effects are most clearly seen when looking at Figures 1 and 2. During the dark cycles, you can see that the distance moved for the fish that were exposed to any concentration of Ropinirole (1, 10, 100 μM) is significantly lower than the distance moved for the controls (ERM, DMSO, and Domperidone).
As a bonus, you can see that out of the 3 Ropinirole concentrations, the lowest dose of Ropinirole (1 μM Ropinirole) had the most distance traveled, followed by the medium concentration ( 10 μM Ropinirole), and finally the highest concentration (100 μM Ropinirole). This pattern led me to my conclusion that as the concentration of Ropinirole increased, the total distance traveled decreased, indicating hypoactivity among the fish that were exposed to Ropinirole.
Hope that answered your question!
Really interesting research, just curious why this exact fish was tested and why at such an early age.
Thanks for your question. Just left an extended response to Dominika’s post, who had a similar question to yours. See above.
Hi Andrew, super interesting presentation!
Why is Domperidone a positive control in this experiment and what is it normally used to treat?
Similar to how Ropinirole is a dopamine receptor agonist, Domperidone is a receptor antagonist, suggesting that it would have the opposite effect of Ropinirole and is why it was used as a positive control. If I hypothesized that an exposure to Ropinirole would induce hypoactivity, then as the positive control, an exposure to Domperidone would induce hyperactivity, which is exactly what happened in my experiment, as indicated by the graphs on my poster.. Clinically, it is given as a medication that increases stomach and bowl movements and is sometimes given to Parkinson’s Disease patients that are experiencing nausea and vomiting as a side effect from other drugs.
Here is a paper on the effects of Domperidone on larval zebrafish that the Martyniuk Lab published a couple of years ago and inspired me to do this Ropinrole project!
This presentation was quite wonderful. The use of Ropinirole in this experiment was quite interesting. I wonder what this research implies for dopamine receptors in humans.
Thanks for checking out my project! I believe that the research conducted on dopamine receptors in this experiment translates quite well to humans! While this particular experiment focused mainly on the locomotor and behavioral aspects of the Ropinirole exposure, I am currently doing experiments on the genetic effects as well. Specifically, I am looking at what genes are expressed within these zebrafish while being exposed to Ropinirole. I think the conclusions made from that experiment would have more substantial implications on dopamine receptors within humans.