Sympathetic regulation of the cardiovascular system is required to maintain cardiac output and vascular tone in response to varied physiological stressors. This includes the release norepinepherine and epinephrine. Nor/epinephrine acts on nine, evolutionarily conserved, adrenergic, G-protein coupled receptors. Three alpha 1 ( Adra1 ), 3 alpha 2 ( Adra2 ), and 3 beta ( Adrb ) receptors. Understanding the distribution and cell-specific function of each of these receptors may lead to new targeted therapies for cardiovascular disease. To delineate the relative roles of each of the 9 adrenergic receptors, we are taking a genetic approach to study these receptors in mice; specifically, by using the Cre-loxP system to target the varied receptors in a tissue-specific manner. Unfortunately, there is a dearth of such tools to study these receptors. We therefore are in the process of generating three sets of tools for each of the 9 adrenergic receptors using the CRISPR-Cas9 method. 1. Adrenergic receptor floxed mice. 2. Adrenergic receptor reactivation (transcriptional blocking) mice and 3. Adrenergic receptor Cre mice. Thus far, we have generated Adra1a , Adra1b , Adra1d , Adra2a , Adrb2 , and Adrb3 floxed mice by inserting loxP sites flanking at least one exon near the 5’ end of the gene. The floxed mice were crossed to a germline-Cre (CMV-Cre), generating mice with whole-body loss of function alleles. Complementing the conditional loss of function alleles, we are also generating reactivation alleles by inserting a loxP-flanked transcriptional blocking cassette (TB) in each of the 9 endogenous adrenergic receptor genes. These TB alleles will allow us to reactivate endogenous expression of each adrenergic receptor in a Cre-dependent manner in an otherwise global knockout background. This model will allow us to identify tissues which are sufficient for the function of each adrenergic receptor. Finally, the ires-Cre models will allow for targeting of each adrenergic receptor-expressing cells with genetic reporters, and physiological studies using chemo and/or optogenetics. These new tools will assist in identifying the site of action and physiological function of various receptor subtypes and provide mechanistic insights into adrenergic receptor signaling.