A recent study conducted by Carlee Toddes, a graduate student in the lab of Patrick Rothwell PhD, an assistant professor in the Department of Neuroscience at the University of Minnesota Medical School, discovers the importance of the brain’s opioids in the expression of social behavior. 

Published in the Journal of Neuroscience, the study investigates the social behavior of mice who either had a full or partial loss of mu opioid receptors.

“In humans, social interaction is essential for mental health and can become disrupted by various neuropsychiatric disorders,” Toddes said. “I focused my thesis research on how manipulation of the mu opioid receptor system affects the expression and reward valuation of social interaction in mice, another prosocial species with highly conserved brain regions to humans.” 

Toddes is first author of this study. While currently pursuing her PhD in neuroscience at the U of M Medical School, she has been working with Dr. Rothwell as a graduate research assistant for several years. She shared that her partnership with Dr. Rothwell has grown her passion for studying social behavior and, particularly, the impact that neural circuits have on social behaviors. 

The data show that the partial loss of signaling by opioid receptors can alter brain structure and function and impair social behavior of mice, highlighting a key role for the brain's own (endogenous) opioids in the formation of social bonds.

The results of the study found that mice with the partial reduction in mu opioid receptors did not find reward in social interactions when compared to the mice with normal levels of mu opioid receptors. 

Toddes shared that this understanding of the importance of the mu opioid receptors can assist in providing therapeutic targets for individuals struggling with social impairments. 

Toddes and Dr. Rothwell worked with a team of several researchers and received funding to do the study from the National Institute of Mental Health and the National Institute on Drug Abuse.