Sensory and Opioid Mechanisms of Affective Touch

Background: Medicines called opioids are used to treat pain. The body also produces opioids. These are called endorphins. Researchers want to learn more about how these natural opioids work. This might lead to new therapies for conditions like depression, anxiety, and chronic pain. Objective: To determine how opioids affect how pleasant or unpleasant it feels when the skin is touched, compressed, or heated. Eligibility: Healthy right-handed adults ages 18-50. Design: Participants will be screened under another protocol. Participants will have 2 study visits with the same procedures, at least 1 day apart. Each visit will last 3-4 hours. Participants will wear shorts or change into scrubs so researchers can test on their legs. Participants will answer questions and have urine tests. Participants will have a brain magnetic resonance imaging (MRI) scan. The scanner is a metal cylinder in a strong magnetic field. Participants will lie on a table that slides in and out of the cylinder. A device called a coil will be placed over the head. During MRI, participants will have sensory testing. They will get several types of touch to the calf of the leg. These include gentle brushing of the skin, gentle compression of the calf with an inflation sleeve, and heat stimuli. Participants will have an intravenous line placed each day. They will get naloxone 1 day and saline the other day. Participants will not be told which they get. Naloxone is a drug that blocks opioid receptors. The MRI and sensory testing will then be repeated. After each stimuli block, participants will rate the sensations as well as their mood and calmness/anxiety.