“It combines my interests of biology and psychology”: The Effects of Thiamethoxam Pesticide on In Utero Rats

(Photos provided by Alexis Wood)

“I am fascinated with the idea that I could discover something that no one else in the world knows yet. Since thiamethoxam has such a wide range of applications, the findings from this study will be deeply impactful.” ~Alexis Wood

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*In the following interview, TS refers to The Synapse and AW refers to Alexis Wood;

TS: Could you briefly introduce yourself, your supervisor, the topic of your thesis, and the field it contributes to?

AW: My name is Alexis Wood and I am a Biology Major with a Minor in Psychology at the University of Prince Edward Island. My Honours thesis supervisor is Dr. Andrew Tasker, who is a professor and researcher of neuropharmacology in the Biomedical Research department at the Atlantic Veterinary College.

I am really excited about my Honours Thesis with Dr. Tasker because it combines my interests of biology and psychology. My thesis investigates the behavioral and molecular effects of thiamethoxam, a neonicotinoid pesticide, on in utero rats. The objective of this research is to determine if exposure to thiamethoxam in utero results in long-term detrimental effects on central nervous system function. This study may help contribute to policy changes regarding the use and regulations of neonicotinoid pesticides.

TS: What is the inspiration for your study, and the research question(s)?

AW: Agriculture on Prince Edward Island is a traditional industry that makes significant economic contributions to the province. Growing up on a farm in rural Prince Edward Island, I learned from a young age the importance of pesticides for safely managing pests such as insects, fungi, and weeds which may threaten the quality and health of crops. I also learned the importance of following pesticide regulations set by the Health Canada Pest Management Regulatory Agency to protect human health and the environment.

When Dr. Tasker had proposed my research project to me, which is one part of an NSERC Discovery grant, I was very interested in broadening my perspective and understanding of neonicotinoid pesticides.

Neonicotinoid insecticides have become the most widely used insecticide in the world since their introduction in the 1990s. Particularly, thiamethoxam is a neonicotinoid insecticide that has been approved for use for over 10 years. These insecticides are used in a variety of settings including agricultural, commercial, residential, and veterinary settings. Neonicotinoids are used in seed treatments, soil applications, foliar spray on agricultural crops such as oilseeds, grains, pulse crops, fruits and vegetables, as well as pet care products for flea control. Thiamethoxam uniquely causes motor paralysis and death in insects by activating neuromuscular nicotinic acetylcholine receptors (nAChRs), which are associated with heart rate and muscle contraction.

For humans and environmental health, these compounds have been determined to be safer. However, previous studies provide evidence that neonicotinoid pesticides harm more than just their target insect species. It has been widely speculated that neonicotinoids are a major contributor to the catastrophic decline in pollinators. There is growing evidence that vertebrate wildlife is also affected: the consumption of dressed seeds (i.e. seeds contaminated with pesticide) can increase mortality in birds and other mammals. Additionally, these chemicals will remain in the environment for decades, yet few studies exist on the effects that sublethal concentrations of neonicotinoids have on mammalian behavior. My research project will help fill this gap in the literature by assessing behavior abnormalities in rats that are exposed to the pesticide in utero.

TS: Could you provide a brief summary of the methods or experimental procedure used in this study?

AW: Timed pregnant Sprague Dawley rats will be treated with thiamethoxam or saline solution for 7 days after gestational day 14, which corresponds to a critical point in the maturation of the rat nervous system. Saline solution was used in control rats to account for the invasive surgical procedures undergone by the experimental rats for insertion of thiamethoxam.

Behavioural abnormalities in both male and female offspring will be investigated using a comprehensive battery of physical, sensorimotor, emotional, and cognitive tests. Behavioural testing will take place from birth until 75 days of age.

The behavioural study will be complemented by immunochemical analyses of relevant receptor subunits. Specifically, the cortex and hippocampus will undergo Western blot analysis to detect three proteins: 1) glutamate NMDA receptor subunit (NR1); 2) nicotinic receptor subunit (α4); and 3) GABA- A receptor subunit (α1). These receptors play an important role in psychomotor excitation (NMDA), inhibition (GABA-A) and cognition (α4).

TS: What are the main results you observed or expect to see?

AW: Currently, I am just finishing up the neurobehavioural testing component of the study. I will begin Western blotting in early 2023.

It will be interesting to analyze the results. Based on the previous literature, I am interested to see if neonates exposed to thiamethoxam in utero will experience delayed development and abnormal maturation of the nervous system.

TS: What would you consider the most intriguing part of the research process?

AW: I think the most intriguing part of the research process is the thrill of embarking on new discoveries. Although I spend many of my days standing in a behavioural testing chamber with rodents, I am fascinated with the idea that I could discover something that no one else in the world knows yet. Since thiamethoxam has such a wide range of applications, the findings from this study will be deeply impactful.

TS: Is there anything else you wish to share about the research experience/ study?

AW: I have had such a positive experience doing research throughout my undergrad. My greatest advice for any students' even remotely considering research is to send that email to a faculty member of interest or to attend that information session on research opportunities on campus. I sent an email to Dr. Tasker after my first year of university and he, along with the lab manager Debra Macdonald, have become some of my greatest mentors. My first experience working in Dr. Tasker's lab was through an NSERC USRA grant and I am now continuing that project as part of my Honours thesis. Ψ

Created for The Synapse by Incé Husain.