Elucidating Differential Expression of Mu Opioid Receptor in Noradrenergic Locus Coeruleus Neurons by Sex (2024)

Undergraduates: Samuel Hendrix, Melissa Medina, Katrina Souter, Emily Liu

Faculty Advisor: Sabrina Robertson
Department: Neuroscience & Psychology

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Norepinephrine is an abundant neurotransmitter in the central and peripheral nervous system, especially in the Locus Coeruleus. As it is so widespread, norepinephrine is vital for modulating several functions, most notably in the “reward and feeding” pathway. Because of norepinephrine’s key role, abnormalities in expression can have implications for neural disorders such as drug addiction. Mu opioid receptors (MORs) are a type of G-protein-coupled receptor (GPCR) that regulate pain responses, rewards, and neuronal excitability. MORs are directly connected to the body’s opioid response and their expression is vital in the efficacy of opioids for pain management. As such, understanding what factors alter the expression of MORs may lend insight into how opioids are utilized. Our study aims to understand how the expression of MOR in NE nuclei may differ between genders using immunohistochemistry. The immunohistochemistry in this experiment was used on transgenic mice to stain NE nuclei green and MORs red to look for overlap in the LC between male and female mice. Mouse brains were collected post-mortem for tissue preparation and imaging using fluorescent microscopy. The data collected from microscopy was analyzed and tested for statistical significance. We expect our findings to show differential expression of MOR across NE neurons in the LC, with greater expression in females. These findings shed light on the potential sex differences in vulnerability to opioid addiction or withdrawal and may contribute towards the development of sex-specific opioid drug treatments.