PROJECT SUMMARY Fetal growth restriction (FGR) increases the risk of stillbirth and neonatal death. The adverse effects of being born FGR extend well beyond the perinatal period, increasing the risk of cardiovascular disease, among others, in later life. Impaired vascular adaptation to pregnancy is a predominant contributor to FGR. Hypoxic conditions also alter uteroplacental vascular function, reducing fetal growth, similarly to FGR. To understand the mechanisms by which an increase in uterine artery (UtA) blood flow can prevent hypoxia-dependent impaired uterine vasculature and reduced fetal growth, we propose using optogenetics and chemogenetics technology for manipulating uterine blood flow in live animals. Optogenetics is an innovative technique in which genetically modified cells express light-activated microbial opsins (e.g., halorhodopsin [NpHR]), which can then be selectively stimulated by light in vivo. Chemogenetics utilizes modified receptors such as the muscarinic M3 receptor (hM3Dq), which can be selectively activated by specific agonists (e.g., deschloroclozapine [DCZ]). Our goal is to develop novel and reliable murine models to prevent FGR via endothelium or smooth muscle-specific mechanisms in the UtA. To address this goal, we propose to conduct two scientific aims. In Aim 1, in mice expressing NpHR in the smooth muscle, we will address the capacity for light stimulation to vasodilate the UtA in vivo, increasing UtA blood flow and preventing FGR. Aim 2 will determine the effect of endothelium-dependent UtA vasodilation via expression of hM3Dq and its selective activation by DCZ locally applied through a microfluidic channel. Current murine models for increasing UtA blood flow in vivo require pharmacological activations that are non-tissue specific, and the timing of the activation cannot be controlled. Our optogenetic and chemogenetic models will provide better control of the degree of blood flow manipulation, enhanced reproducibility among experiments, improved selectivity of the stimulation, and the opportunity to test the timing of stimulation. This project will be the first to apply optogenetics and chemogenetics to the vasodilation of UtA in vivo. Importantly, our proposal can provide the foundation for applying optogenetics and chemogenetics to the study of other vascular beds in vivo.