The Potential Protective Role of Communal Nesting on the Behavioral Consequences of Prenatal Infection in Mice

Prenatal infection is an early life-disturbance that increases the risk for poor mental health in adulthood. Early pregnancy is a critical period for fetal brain development and infection during this period may play a role in the etiology of many neuropsychiatric disorders. In rodents, it is well established that prenatal treatment with lipopolysaccharide (LPS), a bacterial endotoxin, disrupts fetal brain development and increases behaviors associated with anxiety, depression, and poor cognitive performance on memory-related tasks in adult offspring. However, infection during early pregnancy does not guarantee the onset of mental illness. Early-life environments can interact with biological predispositions to influence mental health. In rodents, communal nesting (CN) is a form of environmental enrichment that increases sociability and neurogenesis, both of which have been suggested to support emotional regulation and cognitive function. It is currently unknown if the benefits associated with CN can attenuate the effects of prenatal infection in mice. Therefore, the current study investigated the effect of CN on adult mouse offspring exposed to LPS during early gestation. It was hypothesized that CN would nullify or decrease the effects of prenatal LPS on anhedonia and recognition memory performance. For anxiety, it was hypothesized that CN would increase anxiety-like behavior compared to SN. For all behavioral measures, differences between males and females were also analyzed. Results show that LPS did not induce anxiety and depressive-like phenotypes in offspring. Also, there were no difference between CN males and females for anhedonia, but SN decreased anhedonia in males only. Furthermore, LPS enhanced recognition memory on the novel object task in SN offspring and CN enhanced memory in males. For anxiety, males showed less anxiety-like behavior by traveling greater distances in the open compared to females. Nesting condition also affected anxiety as SN offspring spent more time in the open and were more exploratory than CN offspring. The results of the current study suggest that CN and SN environments sex-dependently alter behaviors relevant for cognitive and affective states within each nesting group while LPS in early gestation does not impair recognition memory.