Examining the impact of neuroimmune dysregulation on social play behavior of male and female juvenile rats

Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
There are many neurodevelopmental disorders associated with altered social behavior in humans. Current literature indicates that along with many genetic risk factors there are also environmental factors that contribute to the risk of developing neurodevelopmental disorders, including those with disordered social behavior. These environmental factors are known to activate the immune system. Various environmental factors (infection, pollution, drugs) and their associated dysregulation of the immune system in early life may in fact have negative consequences on neural function and social behavior. In the current project, we examined the impact of neonatal infection, with or without juvenile immune activation, on the expression of social behavior, and dopamine receptor expression in male and female test juvenile rats. We modeled disordered social behavior in a test animal and scored a typical social interaction (play behavior) from the point of view of the test animal. This was done by coding for behaviors initiating a play bout by test as well as behaviors that indicated participating in a play bout. ☐ The outcomes of these experiments revealed that neonatal infection significantly increased juvenile play behavior in male and female test rats. Moreover, we saw that the test rats showed increased instances of initiating a play bout rather than participating. According to the two-hit hypothesis of neuroinflammation, increases in dopamine receptors and changes in behavior should be most robust in rats exposed to both an early-life and later-life immune challenge. Within the current project this hypothesis was sometimes true, however, the molecular data indicates that neonatal infection alone led to significant differences in dopamine receptor expression within the juvenile brain. The outcomes of these experiments revealed that neonatal infection significantly decreased dopamine relative gene expression, but significantly increased dopamine receptor density. Taken together, the behavioral and molecular data support the sensitivity of the juvenile brain to immune activation (both with and without neonatal infection), especially in the expression of species typical social behavior. Thus, environmental factors that activate the immune system during development are likely significant risk factors for neurodevelopmental disorders in human children.
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Keywords
Neonatal infection, Social behavior, Dopamine receptor expression
Citation