Last updated on September 2018

Sensory and Opioid Mechanisms of Affective Touch


Brief description of study

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.

Detailed Study Description

Objective: Our recent pilot study found evidence suggesting that blocking endogenous opioid release increases the pleasantness associated with having the skin stroked. Deep pressure touch (observed in hugs and massage) also typically conveys a sense of pleasantness. This increased pleasantness contrasts with evidence that blocking endogenous opioid release increases pain. The current study will examine the role of endogenous opioids in the pleasantness of light skin stroking and deep pressure touch, and contrast it with their role in the unpleasantness of a painful heat stimulus. Further, it will examine the neural basis of observed perceptual changes, using fMRI. This study constitutes the first study of the K99 phase of a K99/R00 grant application recently submitted to NCCIH by Dr. Laura Case.

Study Population: 30 healthy participants will be enrolled in the study.

Design: Participants will receive intravenous saline or intravenous naloxone on separate days to investigate the effect of mu-opioid antagonism on the intensity and pleasantness of superficial and deep affective touch and the intensity and unpleasantness of cutaneous heat pain. Using a double-blind cross-over design, functional Magnetic Resonance Imaging (fMRI) will be conducted during sensory testing before and after the infusion of each drug to examine the neural mediation of opioid effects on touch perception. Ratings of mood, anxiety, pain intensity, pleasantness/unpleasantness, wanting and liking will also be collected throughout the study session.

Outcome measures: We will compare subjective ratings (mood, calmness, anxiety, pleasantness, wanting, liking, pain intensity and unpleasantness) during naloxone and saline to: 1) Determine whether naloxone increases the pleasantness and/or intensity of affective touch (light brush and deep compression); 2) Determine whether naloxone increases the unpleasantness and/or intensity of cutaneous heat pain; 3) Determine the role of mood or anxiety changes in mediating the effect of endogenous opioids on these perceptual measures; 3) Determine changes in the brain activation related to these effects.

Clinical Study Identifier: NCT03096353

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National Institutes of Health Clinical Center
Bethesda, MD United States
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