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

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 mu-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.