ATLANTA--Georgia State University researchers have been awarded a five-year, $2.7 million grant from the National Institute of Mental Health to investigate how oxytocin and dopamine act in the reward circuits of the brain to make social interactions rewarding for males and females.
The project is led by Elliott Albers, Regents' Professor in the Neuroscience Institute (NI) and Director of the university's Center for Behavioral Neuroscience (CBN). Kim Huhman, Distinguished University Professor of Neuroscience and associate director of the CBN, is co-principal investigator.
The project could provide new mechanisms for understanding well-known sex differences in the incidence of neuropsychiatric and neurodevelopmental disorders for which dysfunctional social relationships or social avoidance are an important symptom, such as in autism spectrum disorder or depression. It also has the potential to spur the development of gender-specific treatments for these disorders.
The rewarding properties of social interactions are critical to the expression of adaptive social behavior and for the formation of social relationships. Little is known, however, about the factors that determine the reward value of social interactions, the basic neural mechanisms that underlie social reward, particularly in females, or how an individual's status within a hierarchical social relationship influences social reward.
Albers' lab was the first to demonstrate in male rodents that the activation of oxytocin receptors in the brain's reward circuitry is necessary for social interactions to be rewarding. Oxytocin is a hormone produced in the brain that plays a role in social bonding and social behavior.
"If you went to a party where people were enjoying themselves and oxytocin activity was suddenly blocked in the brain, everyone would lose interest in socially interacting and just want to go home," Albers said.
The team is studying the role of oxytocin and dopamine, a neurotransmitter that affects reward-motivated behavior, in regulating social reward in males and females. Based on their earlier work, the researchers have hypothesized there is an inverted U relationship between the dose of social interactions and social reward. As the intensity of interactions increases, so does the reward -- but only up to a point. The outcome of past social interactions also greatly influences interest in engaging in future interactions.
"If social interactions are too intense, they start to become less rewarding and eventually become aversive," said Huhman. "In addition, past experience of being a winner or loser in a social hierarchy appear to change the brain to alter the rewarding properties of social interaction."
The researchers have also hypothesized that females find smaller doses of social interaction more rewarding than do males and the aversive effects set in earlier for females than for males. Researchers will begin by documenting the relationship between the intensity of social interaction and the rewarding properties of those interactions in males and females using Syrian hamsters. The team will then use advanced approaches to manipulate chemical systems in the brain to investigate whether observed sex differences are mediated by differences in oxytocin and dopamine activity in the reward circuitry.
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