Effects of Vagal Dysfunction on Gastrointestinal and Inflammatory Pathways in HIV

This study is investigating how HIV affects the vagus nerve — the nerve that connects the brain to the gut and helps regulate digestion and inflammation. Researchers want to understand whether damage to this nerve (called vagal dysfunction) contributes to digestive problems and immune system inflammation in people with HIV, even those whose virus is well controlled. **You may be eligible if:** - You are 18 years or older - You have documented HIV-1 infection - You have been on stable HIV treatment (ART) for at least 3 months - Your HIV viral load is below 100 copies/mL (well controlled) - You do not have other conditions known to affect the nervous system or digestive system (such as Parkinson's disease, diabetes, or active infections causing diarrhea) - You are willing to avoid nicotine for 24 hours before each test **You may NOT be eligible if:** - You have uncontrolled glaucoma or an irregular heartbeat not controlled by the heart's natural rhythm - You are taking medications that significantly affect the nervous system or digestive system - Your urine test is positive for stimulants or opioids - You are pregnant Talk to your doctor to see if this trial is right for you.