Thesis Format
Monograph
Degree
Master of Science
Program
Chemistry
Supervisor
Yeung, Ken
Abstract
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is an analytical technique used to visualize the spatial distribution of molecules within biological samples. In our lab, we employ two complementary matrices, 2-fluoro-1-methyl pyridinium (FMP-10) and zinc oxide nanoparticles (ZnO NP), to image neurotransmitters in rodent brain tissue. FMP-10 facilitates on-tissue chemical derivatization to detect 17 neurochemicals, notably dopamine, γ-aminobutyric acid (GABA), serotonin, and norepinephrine. ZnO NP detects 9 neurochemicals, including glutamate and glutamine, which are undetectable by FMP-10.
We applied both matrices to investigate neurochemical changes in male and female adolescent rats administered edible Δ-9-tetrahydrocannabinol (THC). Our MALDI MSI data revealed significant downregulation of dopamine, GABA, glutamate, and glutamine levels in the prefrontal cortex and nucleus accumbens of THC-treated males and females. To improve the quantitative accuracy of our MALDI MSI analysis, we evaluated deuterated GABA (GABA-d6) as an internal standard to achieve precise and reproducible quantitation of molecules.
Summary for Lay Audience
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is a scientific method researchers use to visualize where specific molecules, such as neurotransmitters (chemical messengers in the brain), are located within biological samples, like brain tissue. By studying the distribution of these molecules, scientists gain insights into how diseases affect the brain and how treatments might work.
To perform MALDI MSI, a special chemical called a “matrix” is applied to the tissue sample to help detect these molecules. In our lab, we use two different matrices: FMP-10 and zinc oxide nanoparticles (ZnO NP) to study neurotransmitters in rodent brain tissue. FMP-10 can detect 17 different neurotransmitters, including dopamine (involved in mood), GABA (which helps calm the brain), serotonin (linked to happiness), and norepinephrine (involved in stress responses). ZnO NP detects 9 other neurotransmitters, like glutamate and glutamine, which FMP-10 cannot. By using both matrices, we can identify 26 different neurotransmitters in rat and mouse brain tissues.
We used this technique to study the effects of THC (the main psychoactive ingredient in cannabis) when consumed during adolescence. We gave adolescent male and female rats THC mixed with Nutella® and imaged their brains. Our MALDI MSI results showed reduced levels of key neurotransmitters, like dopamine, GABA, glutamate, and glutamine, in important brain regions involved in decision-making and rewards. This suggests that adolescent THC use could disrupt normal brain function and lead to mental health problems later in life.
While MALDI MSI is very good at detecting neurotransmitters, measuring the exact amounts can be difficult. To address this, we used a GABA-d6 internal standard. This standard acts as a reference, helping us accurately compare and correct the signals from the neurotransmitters, ensuring that our data is reliable.
Recommended Citation
Pusparajah, Mathusha, "Detection and Imaging of Neurotransmitters in Rodent Brain Tissue Using FMP-10 and ZnO Nanoparticle Matrices with Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry" (2024). Electronic Thesis and Dissertation Repository. 10489.
https://ir.lib.uwo.ca/etd/10489