This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In this protocol, the investigators will test the isolated and combined effects of regional blockade of adenosine (with the adenosine-receptor inhibitor aminophylline), nitric oxide (with nitric oxide synthase inhibitor NG-monomethyl-L-arginine, L-NMMA) and prostaglandin (with prostaglandin synthesis inhibitor ketorolac) pathways on limb blood flow during exposure to systemic hypoxia.