The Effects of Parity and Maternal Behavior on Gene Expression in the Medial Preoptic Area and the Medial Amygdala in Postpartum and Virgin Female Rats: A Microarray Study Emis M. Akbari University of Toronto Soaleha Shams, Hiwote T. Belay, Mo Kaiguo, and Zak Razak University of Toronto at Mississauga Clement F. Kent York University Tim Westwood University of Toronto at Mississauga Marla B. Sokolowski and Alison S. Fleming University of Toronto To determine the pattern of gene expression in brains associated with mothering during the postpartum period, in the present study we assessed gene expression through microarrays in four groups of female rats: two groups of new mothers that were experiencing the hormonal and neurochemical changes associated with pregnancy and parturition, and two groups of virgin females that were not. Within each of these parity groups we assessed one group of animals that was exposed to and responded to pups and engaged in maternal behavior, and one group left without any exposure to pups and therefore had no maternal experience. We explored the pattern of expression of genes related to the hormones, neurotransmitters, and modulatory neuropeptides associated with maternal behavior within the medial preoptic area (MPOA) and the medial amygdala (MeA) in the rat. Within the MPOA there were significant main effects of pup exposure for the dopamine-related genes (DRD4 and dopamine transporter, DAT), the glucocorticoid-related gene (CYPX1B1a), the opioid receptor -1 gene (OPRM1) and the gamma-aminobutyric acid (GABA) receptor gene (GABAbRid). OPRM1 and the serotonin-related gene that regulates biosynthesis of serotonin (5HTR2A) showed a main effect of parity. For both sets of analyses, higher gene expression was associated with pup exposure and parity. Genes expressed in the MeA tended to reside in the glucocorticoid family. The microarrays were able to identify, on a transcriptional level, a list of candidate genes involved in maternal behavior and the factors that surround it. Keywords: Limbic, dopamine, hypothalamus, RNA, mother Supplemental materials: http://dx.doi.org/10.1037/a0034884.supp Many hormones and neurotransmitters are implicated in the onset and expression of maternal behavior, acting at multiple sites in the brain and affecting a variety of behavioral systems (Numan, Fleming, & Levy, 2006). The levels of these hormones and neurochemicals result from genes that are expressed in the brain and organ systems during parturition and in the early postpartum period. We focus on expression of candidate genes known to play a role in mothering, either through the new mother’s endocrine state or in response to pup stimulation. Emis M. Akbari, Department of Psychology and Fraser Mustard Institute for Human Development, University of Toronto, Toronto, Ontario, Can- ada; Soaleha Shams, Department of Psychology, University of Toronto at Mississauga, Mississauga, Ontario, Canada; Hiwote T. Belay, Mo Kaiguo, and Zak Razak, Department of Biology, University of Toronto at Missis- sauga, Mississauga, Ontario, Canada; Clement F. Kent, Department of Biology, York University, Toronto, Ontario, Canada; Tim Westwood, Department of Biology, University of Toronto at Mississauga, Missis- sauga, Ontario, Canada; Marla B. Sokolowski, Department of Ecology and Evolutionary Biology and Fraser Mustard Institute for Human Develop- ment, University of Toronto, Toronto, Ontario, Canada; Alison S. Fleming, Department of Psychology and Fraser Mustard Institute for Human De- velopment, University of Toronto, Toronto, Ontario, Canada. Research was supported by grants from Natural Sciences Engineering and Research Council (NSERC) and the Canada Research Chair Pro- gram to Alison S. Fleming, the Canada Research Chair Program and the Canadian Institute for Advanced Research to M. B. Sokolowski, and the Global Connaught grant to both Fleming and Sokolowski. Research was completed in the behavioral, genetic, and microarray laboratories of Fleming, Sokolowski, and Westwood, respectively and in equal mea- sure. Correspondence concerning this article should be addressed to Alison S. Fleming, Ontario Institute for Studies in Education, Fraser Mustard Insti- tute for Human Development, University of Toronto, 252 Bloor Street West, 7th Floor, Toronto, Ontario, M5S 1V6 Canada. E-mail: alison .fleming@utoronto.ca This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Behavioral Neuroscience © 2013 American Psychological Association 2013, Vol. 127, No. 6, 913–922 0735-7044/13/$12.00 DOI: 10.1037/a0034884 913