Seminal Plasma Triggers the Differential Expression of the Glucocorticoid Receptor (NR3C1/GR) in the Rabbit Reproductive Tract

Simple Summary Glucocorticoids are steroid hormones modulating different functions in mammals, including reproduction, that act through the glucocorticoid receptor, encoded by the gene called NR3C1. Here, we describe how the expression levels of the glucocorticoid receptor change along the different compartments of the female rabbit internal reproductive tract 20 h after insemination with sperm-free seminal plasma or natural mating (whole semen) (Experiment 1) and how these levels change at 10, 24, 36, 68, and 72 h post-mating, during specific stages over time, i.e., ovulation, fertilization and the interval of early embryo development to the morula stage occurs (Experiment 2). NR3C1-upregulation was found in the infundibulum at 20 h after all treatments, especially after sperm-free seminal plasma infusion compared to mating (Experiment 1). In Experiment 2, the receptor gene expression levels increased in a spatio-temporal sequence, corresponding to the assumed location of the rabbit embryos (particularly morulae) in the oviductal various segments and timepoints (particularly 72 h), compared to down-expression at uterine regions. We conclude that NR3C1 may play a relevant role in the rabbit female reproductive tract. Rabbits are interesting as research animal models for reproduction, due to their condition of species of induced ovulation, with the release of endogenous gonadotropin-releasing hormone (GnRH) due to coitus. Glucocorticoid (GC) signaling, crucial for physiological homeostasis, is mediated through a yet unclear mechanism, by the GC receptor (NR3C1/GR). After mating, the female reproductive tract undergoes dynamic modifications, triggered by gene transcription, a pre-amble for fertilization and pregnancy. This study tested the hypothesis that when ovulation is induced, the expression of NR3C1 is influenced by sperm-free seminal plasma (SP), similarly to after mating (whole semen), along the different segments of the internal reproductive tract of female rabbits. Semen (mating) was compared to vaginal ...