Activating the Cholinergic Anti-Inflammatory Pathway in Healthy Volunteers and People With Inflammatory Arthritis

Healthy Volunteer Population Inclusion Criteria: * 22-75 years of age * Weigh at least 40 kg Exclusion Criteria: * Any physical disabilities, conditions, or diseases that limit the capacity to participate in study procedures or increase the risk of harm as determined by the study PI * Unable to provide informed consent * Active bacterial or viral infection * Class II obesity with a BMI of 35 or higher * Pregnant women or those trying to become pregnant * Active use of tobacco/nicotine products * History of substance use disorder or active regular use of substances (nicotine, marijuana, cocaine, psychedelics, stimulants, etc.) * Splenomegaly, asplenia, or splenectomy Inflammatory Arthritis Population Inclusion Criteria: * 22-75 years of age * Weigh at least 40 kg * Diagnosis of Rheumatoid Arthritis, Psoriatic Arthritis, or Axial Spondyloarthritis of at least 6 months duration as defined by ACR guidelines * Able to continue the same stable dose of immunomodulatory medication(s) while participating in the study Exclusion Criteria: * Unable to provide informed consent * Took a JAK inhibitor within the last 4 weeks, or likely to start one while participating in this study * Started a conventional synthetic DMARD (csDMARD) within the last 8 weeks or had a change in prescription within the last 4 week * Started a Tumor Necrosis Factor (TNF) inhibitor within the last 5 months or had a change in prescription within the last 3 months * Started any other biologic or targeted synthetic DMARD within the last 3 months, or likely to start one while participating in the study * Started a corticosteroid, had a change in prescription, or on a stable dose = or \> 10 mg of prednisone daily within the last 4 weeks * Regular use of epinephrine like medications (cold, cough, congestion, or sinus medications, bronchodilators, appetite suppressants) * Active use of tobacco/nicotine products * History of substance use disorder or likely use of substances during the study period (marijuana, opioids/heroin, cocaine, psychedelics, methamphetamine, etc.) * Active bacterial or viral infection * Receiving chemotherapy or immunotherapy to treat malignancy * Significant immunodeficiency due to underlying illness * Class II obesity with a BMI of 35 or higher * Pregnant women or those trying to become pregnant * Wound, rash, infection, or traumatic injury over the target area * Vagal nerve injury or vagotomy * Surgery or major traumatic injury in the past 90 days * Chronically-implanted medical devices (i.e. pacemaker, AICD, vagus nerve stimulator, spinal cord stimulator) * Clinically significant cardiovascular disease * CKD Stage 3 or higher * Uncontrolled fibromyalgia or other diffuse pain syndromes