Periodic maternal deprivation may modulate offspring anxiety-like behavior through mechanisms involving neuroplasticity in the amygdala

Abstract

Maternal care has been shown to affect the development of behavioral and endocrine systems. In rats, periodic maternal deprivation (PMD) serves as an early life stressor that directly influences maternal care by promoting more pup-directed behaviors in stressed dams. To further assess the qualities of PMD that may ameliorate long-term anxiety effects in trait anxiety animals, we coded behaviors across lactation (postnatal day (PND) 5, 16, 21) in dams phenotyped as high (HAn) and low-anxiety (LAn). We assessed anxiety-like behavior in male offspring using the elevated plus maze (EPM), focusing on percent open arm (%OA) time and latency to enter OA (OA LAT) as measures of anxiety-like behavior. Finally, we examined the brains of representative male pups to determine if the stress-related protein brain-derived neurotrophic factor (BDNF) might show persistent changes in the amygdala. Dams phenotyped as HAn had lower %OA time and longer OA LAT relative to dams designated as LAn. During PMD, HAn dams had higher incidences of licking-grooming (L/G) and more pup-directed behaviors on PND 5 and 16 compared to LAn dams. Further, as adults, HAn male offspring exhibited less anxiety traits than their maternal line with greater %OA time and %OA entries relative to LAn. HAn offspring showed markedly more BDNF immunoreacted cells in the amygdala than LAn. The combination of these findings suggests that the mild stressor, PMD alters anxiety-like behavior in offspring likely by influencing HAn dams' L/G activity and altering stress related proteins in the amygdala.