Sensory and Opioid Mechanisms of Affective Touch

-INCLUSION CRITERIA:

All subjects must be:

• Between 18 and 50 years old.
• Right-handed (on Edinburgh Handedness Inventory).
• Fluent in English.
• Able to provide written informed consent.

EXCLUSION CRITERIA:

Overall exclusion criteria for the study:

• Unable to comply with study procedures (or does not rate stimuli as tolerable) or unable to schedule visits promptly (including inability to schedule the second session within approximately 14 days of the first session)
• Pregnancy or breastfeeding.
• Use of recreational drugs in the past month (e.g., marijuana, methylenedioxymethamphetamine (MDMA, 'ecstasy' or 'Molly'), Lysergic acid diethylamide (LSD), cocaine, methamphetamine, heroin, prescription and/or opioids).
• Congenital lower limb deficiency or amputation.
• Peripheral neuropathy, dermatological condition such as scars or burns, or has had a tattoo in the testing region within the previous four weeks that might influence cutaneous sensibility.
• Women who consume more than 7 alcoholic beverages per week, and men who consume more than 14 drinks per week.
• Current chronic pain condition or has had chronic pain in the past year (painful condition lasting more than six months), including ongoing treatment with medications for neuropathic pain (e.g. gabapentin, tricyclic antidepressants, pregabalin, tramadol)
• Major medical condition, such as kidney, liver, cardiovascular (including blood clots, hypertension, preexisting cardiac arrhythmia), autonomic, pulmonary, or neurological problems (e.g., seizure disorder ) or a chronic systemic disease (e.g., diabetes).
• Current diagnosis or pharmacological treatment of psychiatric disorders such as major depression, major anxiety-related problems, post-traumatic stress syndrome, bipolar disorder, psychosis, attention-deficit/hyperactivity disorder or current or lifetime alcohol or substance abuse disorders (as identified in study #16-AT-0077)
• Participant has metal in his/her body which would make having an MRI scan unsafe, such as pacemakers, medication pumps, aneurysm clips, metallic prostheses (including metal pins and rods, heart valves or cochlear implants), shrapnel fragments, permanent eye liner or small metal fragments in the eye that welders and other metal workers may have.
• Participant is uncomfortable in small closed spaces (has claustrophobia) so that he/she would feel uncomfortable in the MRI machine or cannot lie comfortably flat on his/her back for up to 75 minutes in the MRI scanner.
• Participants weighs more than 550 lbs.
• Participant has taken any pain medication other than an over-the-counter NSAIDs or acetaminophen within the last month or for more than one month on a continual basis within last six months.
• Previous participation in 13-AT-0143 (related study).
• NIH employees who are subordinates, relatives, or co-workers of the investigators, or NCCIH Division of Intramural Research (DIR) employees.
• Participants using medications that play into opioid pathways (e.g. loperamide or dextromethorphan), that could potentially interact with naloxone (naltrexone, methylnaltrexone, droperidol, fenfluramine and clonidine)
• Participant using any herbal supplements (such as yohimbine) due to risk of unknown dangerous interaction as there is no data for herbal preparations and naloxone.
• Participant has allergies to naloxone or similar drugs.

EXCLUSION CRITERIA FOR INIDIVIDUAL STUDY SESSION:

• Has consumed alcohol within 24 hours, shows signs of alcohol withdrawal syndrome, or has behavioral signs of intoxication will be excluded immediately and not have the possibility to reschedule their session.

• Used topical pain-relieving creams in the testing area (e.g. methylsalicylate, capsaicin) within 24 hours of testing or used non-steroidal anti-inflammatory drugs (NSAIDS, e.g. aspirin, ibuprofen), acetaminophen, or naproxen within 3 days of testing*.

  • To be determined during the pre-session screening. Participants who cannot refrain from these activities may have their session rescheduled up to two times. If the participant is found non-compliant during the second rescheduled appointment, he or she will be excluded from the study.