Role Of Prolactin Receptor Expression On Pacap Neurons In Thermal Resilience During Pregnancy

Core temperature is a crucial variable needing to be maintained within specific boundaries for cellular function. During pregnancy, core temperature is increased compared to a non-pregnant state. A significant amount of heat is produced from metabolic heat generated by fetal development, with this excessive heat needing to be dissipated to protect core temperature. Core temperature is regulated by specific neurons within the preoptic area, with heat dissipation controlled by warm-sensitive neurons (WSN). Genetic markers for warm-sensitive neurons include BDNF and Adcyap1 (the genetic encoder for PACAP), and recently, single cell sequencing of cells within the POA indicate the likely colocalization of prolactin receptors (Prlr) in WSNs. Unpublished data from our lab has demonstrated that deletion of Prlr in the POA results in higher core temperature during pregnancy, supporting the hypothesis of a thermoregulatory role for POA prolactin receptors. To investigate this hypothesis, our aim was to generate a mouse model with a deletion of prolactin receptors from WSN neurons within the POA. First, we validated the co-expression of prolactin receptor and Adcyap1 mRNA in the POA using RNAscope in situ hybridisation. We found that in the POA approximately 65.2% of Adcyap1 mRNA expressing cells also expressed Prlr and this did not change across pregnancy and lactation. Mice with Prlr deleted from PACAP neurons, were generated by mating Prlr^lox/lox mice with Adcyap1^cre. First, we wanted to explore the deletion of prolactin receptors from PACAP cells in the brains of our transgenic mice. We used GFP as a marker of Prlr deletion as our mouse model featured the expression of GFP in all cells where recombination of the prolactin receptor gene has occurred. GFP immunohistochemistry also served to show us where these two proteins of interest are co-expressed beyond the POA. We found that there was extensive expression of GFP throughout the forebrain indicating deletion of prolactin receptors from PACAP cells and also revealing co-expression in regions of the brain that have not been reported before. Finally, we show that our transgenic mouse model, there are little impacts on pregnancy of prolactin receptor deletion from PACAP cells. Thermal imaging from virgin and pregnant states suggests there may be subtle impacts on thermoregulation in our mouse model warranting further investigation. Altogether, our results indicate there is little impact of prolactin receptor deletion from Adcyap1 neurons on pregnancy, however future studies are needed to confirm this.