Polychlorinated biphenyl exposure alters oxytocin receptor gene expression and maternal behavior in rat model

Abstract

Polychlorinated biphenyl (PCB) is a persistent organic pollutant known to induce diverse molecular and behavioral alterations. Effects of PCB exposure could be transmitted to future generations via changes in behavior and gene expression. Previous work has shown that PCB-exposure can alter social behavior. The present study extends this work by examining a possible molecular mechanism for these changes. Pregnant rats (Sprague-Dawley) were exposed through diet to a combination of non-coplanar (PCB 47 - 2,2′,4,4′-tetrachlorobiphenyl) and coplanar (PCB 77 - 3,3′,4,4′-tetrachlorobiphenyl) congeners. Maternal care behaviors were examined by evaluating the rate and quality of nest building on the last 4 d of gestation and dam/pup interactions on postnatal days 1, 2, 4 and 6. On postnatal day 17, dams were euthanized and hypothalamic tissue was removed for expression analyses of the oxytocin receptor (OXTR) and cytochrome P450 1a1 (Cyp1a1). PCB altered nest building and maternal care behaviors. Specifically, there was a significant increase in time spent in low crouch and high crouch nursing posture on PND 4 and PND 6 respectively. Molecular analysis revealed that PCB exposure upregulated OXTR expression in the hypothalamus of dams. These results provide a possible molecular mechanism for PCB-induced changes in social interactions during early development.

Keywords:

• environmental toxin
• hormones
• hypothalamus
• PCB
• qRT-PCR
• social neuroscience

Acknowledgements

This project was possible because of funding from the National Institute for Child Health and Development (NICHD Grant #053692) and from the JP Scott Center for Neuroscience and Behavior at Bowling Green State University (E.N.D. was a JP Scott Fellow during the 2011-2012 academic year). Experimental work for this project was completed with support from undergraduate Katelyn Ammons and graduate students including Jennifer Benson, Michael Ludwig, Mahesh Pillai, Brian Rutter, Maribeth Spangler, and Zhi Wang.