Impact of fluoxetine treatment and folic acid supplementation on the mammary gland transcriptome during peak lactation

Lactation causes dramatic maternal calcemic adaptations where up to 10% of maternal bone density is mobilized for milk calcium. Serotonin plays a role in regulating this calcemic demand through alterations in DNA methylation. Selective serotonin reuptake inhibitors used to treat peripartum depression exacerbate this signaling. The first objective of this study was to determine the impact of fluoxetine, one of the most popular selective serotonin reuptake inhibitors, on the transcriptome of the mouse mammary gland during peak lactation. The second objective was to determine whether supplementation with folic acid, a well-known methyl donor, would mitigate the gene expression changes induced by fluoxetine. Overall design: Two weeks before mating, C57BL/6 female mice were randomly assigned into breeder diet (4mg/kg folic acid, n = 16) or folic acid supplemented diet (24 mg/kg folic acid, n = 16). Female mice were bred overnight, and pregnancy was determined by observing a seminal plug, at which time the mice were housed individually and randomly assigned to fluoxetine or saline treatment. This resulted in 4 treatments (n = 8 mice per treatment): breeder diet + saline, breeder diet + fluoxetine, folic acid supplemented diet + saline, or folic acid supplemented diet + fluoxetine. Beginning on embryonic day 13 of pregnancy through day 10 of lactation, dams received a daily intraperitoneal injection of either 20 mg/kg bodyweight fluoxetine hydrochloride or saline. At day 10 of lactation, dams were euthanized, and mammary glands were rapidly extracted and stored at -80°C until RNA extraction.