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The Effect of Capsaicin-induced Pain on Homeostatic Plasticity in Healthy Human Participants

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ClinicalTrials.gov Identifier: NCT04485689
Recruitment Status : Recruiting
First Posted : July 24, 2020
Last Update Posted : July 24, 2020
Sponsor:
Information provided by (Responsible Party):
Priscilla G. Wittkopf, Aalborg University

Brief Summary:
People suffering from chronic pain exhibit changes in the way the central nervous system processes pain. Some of the changes in the central nervous system are associated with how the brain adapts to the process of different stimuli. There are several physiological mechanisms that regulates how the brain adapts to changes and one of these mechanisms is called homeostatic plasticity (or equilibrium plasticity ). In healthy participants homeostatic plasticity mechanisms have been tested and considered normal, whereas in patients with chronic conditions, such as low back pain, this mechanism was shown to be dysfunctional. However, it is unknown when this difference in the pain system develops. It is possible that homeostatic mechanism becomes impaired during early stages of pain. This experiment will investigate the effect of capsaicin-induced pain on homeostatic plasticity in healthy participants.

Condition or disease Intervention/treatment Phase
Healthy Drug: Capsaicin Topical Drug: Placebo Not Applicable

Detailed Description:

The aim of this study is to investigate the effect of capsaicin-induced pain on homeostatic plasticity.

A within-subject repeated-measures design will be used to evaluate the effect of capsaicin-induced pain on homeostatic plasticity using cathodal transcranial direct current stimulation (tDCS). Each participant will take part in four experimental sessions during which homeostatic plasticity and corticomotor excitability will be induced and measured in the left primary motor cortex. Participants will receive in randomised order capsaicin or placebo patch placed on the dorsal part of the right hand.

Each participant will attend four sessions, being two consecutive sessions separated by two weeks (i.e. wash-out period). During the experiment, participants will be seated comfortably with hands and arms at rest. First, the electromyography electrodes will be placed at the right hand muscle to be used for assessing the corticomotor excitability by recordings of motor evoked potentials by transcranial magnetic stimulation (TMS) on the left primary motor cortex. Then, the cap for tDCS on the left primary motor cortex will be mounted. The optimal scalp position (hot spot) for TMS stimulation will be identified and marked with a pen on the cap for standardisation. A 5 x 7 cm capsaicin/placebo patch will be placed on participants' right hand. After 30 minutes of patch application, baseline measures of pain and motor-evoked potentials will be taken. Then, the homeostatic plasticity induction process will take place followed by motor-evoked potentials recordings every 15 minutes up to 45 minutes post protocol. Finally, ice will be placed over the patch as to reduce pain intensity to zero and homeostatic plasticity will be induced and measured as previously. The patch will be left in place for 24 hours, at which point participants will return to the laboratory and homeostatic plasticity will once again be induced and measured. After a wash-out period of two weeks, participants will go through an identical process but at this time with a different patch.

Homeostatic plasticity will be induced in the left primary motor cortex using tDCS applied for 7 minutes followed by an interval of 3 minutes and another block of 5 minutes of stimulation. A constant current of 2mA will be transmitted through the tDCS system, using two 25 cm2 electrodes placed into holes of a cap over the hot spot and right supraorbital area.

A sample size calculation was conducted using α of 0.05, β of 0.80 and effect size of 0.29 based on motor evoked potential (MEP) analysis of previous studies resulting in a target of 18 participants.

Data distribution will be assessed using the Shapiro-Wilk test. A repeated measures analysis of variance (ANOVA) will be conducted on mean MEPs with factors Intervention (Capsaicin and Placebo), Time (baseline, 0 min, 15 min, min, 30 min, 45 min) and Time with pain (immediate, post pain relief post prolonged pain). A Greenhouse-Geisser correction will be used if Mauchly's test shows that sphericity cannot be assumed. Adjustments will be made for multiple post-hoc comparisons using the Bonferroni correction. Results will be interpreted according to the level of statistical significance p≤0.05 and effect size reported as partial eta squared.

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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 18 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single (Participant)
Primary Purpose: Basic Science
Official Title: The Effect of Capsaicin-induced Pain on Homeostatic Plasticity in Healthy Human Participants
Actual Study Start Date : July 1, 2020
Estimated Primary Completion Date : December 2020
Estimated Study Completion Date : December 2020

Resource links provided by the National Library of Medicine

Drug Information available for: Capsaicin

Arm Intervention/treatment
Experimental: Capsaicin
5x7 cm2 capsaicin patch
Drug: Capsaicin Topical
5x7 cm2 capsaicin patch applied on the dorsal area of the hand and left in place for 24 hours

Placebo Comparator: Placebo
5x7 cm2 placebo patch
Drug: Placebo
5x7 cm2 patch applied on the dorsal area of the hand and left in place for 24 hours




Primary Outcome Measures :
  1. Conspiratorial excitability [ Time Frame: [Time Frame: 0 minutes post homeostatic plasticity induction] ]
    Corticospinal excitability measured as motor evoked potentials amplitude induced by transcranial magnetic stimulation.

  2. Conspiratorial excitability [ Time Frame: [Time Frame: 15 minutes post homeostatic plasticity induction] ]
    Corticospinal excitability measured as motor evoked potentials amplitude induced by transcranial magnetic stimulation.

  3. Conspiratorial excitability [ Time Frame: [Time Frame: 30 minutes post homeostatic plasticity induction] ]
    Corticospinal excitability measured as motor evoked potentials amplitude induced by transcranial magnetic stimulation.

  4. Conspiratorial excitability [ Time Frame: [Time Frame: 45 minutes post homeostatic plasticity induction] ]
    Corticospinal excitability measured as motor evoked potentials amplitude induced by transcranial magnetic stimulation.


Secondary Outcome Measures :
  1. Pain intensity [ Time Frame: Every 10 minutes post capsaicin application ]
    Pain intensity measured using an 11-point numeric rating scale where 0= no pain and 10 = worst imaginable pain.



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Ages Eligible for Study:   18 Years to 60 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Healthy, aged between 18-60 years, right-handed and can speak and understand English.

Exclusion Criteria:

  • Lack of ability to cooperate
  • Chili allergy
  • History or present chronic pain or current acute pain
  • Pregnancy
  • Drug addiction defined as the use of cannabis, opioids or other drugs
  • Present and previous neurological disorders such as epilepsy, Alzheimer's disease,
  • dementia, stroke, migraine and other headache disorders, multiple sclerosis,
  • Parkinson's disease, neuroinfections, brain tumors and head trauma.
  • Present or previous musculoskeletal disorders such as tendonitis, degenerative disc disease, mechanical back syndrome, and ruptured/herniated disc.
  • Present or previous mental illnesses such as depression, bipolar disorder, and schizophrenia.
  • Current use of medications that may affect the trial (e.g. analgesics, anti- inflammatories, anti-depressives)
  • Contraindications to TMS application (history of epilepsy, metal implants in head or jaw, etc.)
  • Failure to pass the tDCS screening questionnaire
  • Failure to pass the "TASS questionnaire"

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT04485689


Contacts
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Contact: Priscilla G Wittkopf, PhD 311539979 pgw@hst.aau.dk

Locations
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Denmark
Aalborg University Recruiting
Aalborg, Denmark, 9220
Contact: Priscilla G Wittkopf, PhD    +4531539979    pgw@hst.aau.dk   
Sponsors and Collaborators
Aalborg University
Publications:

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Responsible Party: Priscilla G. Wittkopf, Principal Investigator, Aalborg University
ClinicalTrials.gov Identifier: NCT04485689    
Other Study ID Numbers: N-20190069/2
First Posted: July 24, 2020    Key Record Dates
Last Update Posted: July 24, 2020
Last Verified: July 2020
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: No

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No
Additional relevant MeSH terms:
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Capsaicin
Antipruritics
Dermatologic Agents
Sensory System Agents
Peripheral Nervous System Agents
Physiological Effects of Drugs