Itch, Pain
Conditions
Brief summary
The aim of this project is to determine the effects of performing a motor imagery task on cortical excitability during acute experimental muscle pain (induced by hypertonic saline), acute histaminergic itch (induced by histamine), and non-histaminergic itch stimulation (triggered by Cowhage). We hypothesize that motor imagery will counteract the alterations in cortical excitability observed during experimental muscle pain and both itch models.
Detailed description
Itch and pain share many similarities and dissimilarities in terms of the mechanisms and molecules involved. Many studies have been conducted to explain all the neurophysiological aspects involved in the pain process, and cortical adaptations have been provoked in healthy individuals using experimental pain models. Unfortunately, all these aspects still need to be clarified regarding itch. Has been previously demonstrated that motor imagery can counteracted the pain-induced decrease in corticospinal excitability observed during acute pain, and it has also been proposed as a potential intervention for individuals with pain to restore maladaptive neuroplasticity. However, whether motor imagery can similarly counteract the itch-induced cortical changes remains unclear. Therefore, the aim of this project is to investigate whether motor imagery would counteract the reduction in cortical excitability during acute itch, similar to the effects observed in the context of acute pain.
Interventions
OTHERHypertonic Saline
A bolus injection of hypertonic saline (7% NaCl) will be administered to the FDI muscle using a 1 mL syringe with a disposable needle (27G), and the volume of the bolus will be 0.1 mL
OTHERHistamine
A small drop of histamine dihydrochloride will be applied to a previously determined area on the volar forearm, followed by a prick through the drop
OTHERCowhage
This insertion is conducted by forceps using a stereomicroscope, and 30-35 spicules are gently rubbed into a 1 cm diameter skin area.
DEVICETranscranial magnetic stimulation (TMS)
Transcranial magnetic stimulation (TMS) will be used to evoke motor-evoked potentials (MEPs) in the muscle of interest and cortical responses (TMSevoked potentials - TEPs) in the motor cortex with a figure-eight-shaped cone coil.
Sponsors
Aalborg University
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Intervention model description
we apply one of three experimental methods in your hand: either an injection of salt water (7% NaCl) or we apply small needles from the plant mucuna pruriens or histamine (1%)
Eligibility
Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy men and women * 18-60 years * Speak and understand English
Exclusion criteria
* Pregnancy or lactation * Drug addiction defined as any use of cannabis, opioids, or other addictive drugs * Previous or current history of neurological (e.g. neuropathy), immunological (e.g. asthma, immune deficiencies, arthritis), musculoskeletal (e.g. muscular pain in the upper extremities,), cardiac disorder (e.g., heart stroke), or psychiatric diagnoses (e.g. depression) that may affect the results * Current use of medications that may affect the trial, such as antihistamines, antipsychotics, and painkillers, as well as systemic or topical steroids * Skin diseases (e.g., atopic dermatitis, pruritus nodularis, eczema, psoriasis) * Moles, scars, or tattoos in the area to be treated or tested. * Consumption of alcohol or painkillers 24 hours before the study days and between these * Acute or chronic pain * Unable to pass the Transcranial Magnetic Stimulation Adult Safety Screen (subproject 1 and 2) * Contraindications to transcranial magnetic stimulation (TMS) application (history of epilepsy, metal implants in head or jaw, etc.) * Presence of implanted hearing aids or metal implants on the face, including permanent makeup or tattoos * Participation in other trials within one week of study entry (four weeks in the case of pharmaceutical trials) * Lack of ability to cooperate
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Numeric rating scales (NRS) | 1 minute after every itch/pain induction | NRS are essentially VAS but have tick marks spaced every centimeter so as to create 11-point scale (from 0 to 10). Subject can use these tick marks as a guide when they mark their severity on the scale. |
| Measuring cortical excitability (TEPs) | Baseline | Transcranial magnetic stimulation (TMS) with a figure-eight-shaped cone coil will be used to evoke cortical responses in the motor cortex. The resulting TMS-evoked potentials (TEPs) will be collected using an electroencephalogram (EEG). This assessment will last for 7 minutes before inducing itch or pain. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Reinforcement Sensitivity Theory - Personality Questionnaire (RST-PQ). | Baseline | The RST-PQ contains the following subscales: the Fight-Flight-Freeze System (FFFS, 10 items), which represents a defensive factor related to active avoidance of adverse stimuli; the Behavioral Inhibition System (BIS, 23 items), which represents a defensive factor related to anxiety and passive avoidance of adverse stimuli; and the Behavioral Approach System (BAS, 32 items), which reflects reward interest, goal-drive persistence, reward reactivity, and impulsivity. In total, 65 items have to be answered on a 4-point Likert-type scale |
| The Pittsburg Sleep Quality Index (PSQI) | Baseline | The PSQI consists of 19 items generating seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The seven component scores can be summarized in a global score ranging from zero to 21 with higher scores reflecting a worse overall quality of sleep |
| Pain Catastrophizing Scale (PCS). | Baseline | The PCS assesses negative and exaggerated coping concerning anticipated or experienced painful stimuli. Thirteen items have to be answered on a 5-point Likert-type scale. |
| Learned Helplessness Scale (LHS) | Baseline | The questionnaire consists of 20 items, and the participant's response to each item is rated on a 4-point Likert scale ranging from strongly agree (1) to strongly disagree (4). |
| Positive And Negative Affect Schedule (PANAS) | Baseline | PANAS measures positive and negative affect dimensions. Twenty words are associated with the subject's current feelings and have to be rated on a 5-points Likert-type scale. |
| Depression, Anxiety, Stress Scale (DASS-21) | Baseline | The questionnaire measures the magnitude of depression, anxiety, and stress. Each of these three subscales consists of 7 questions answered using a 0-3 Likert scale, with 0 meaning it did not apply to me, and 3 meaning it applied to me very much. |
| Itch Catastrophizing Scale (ICS). | Baseline | The ICS assesses negative and exaggerated coping concerning anticipated or experienced itchy stimuli. Thirteen items have to be answered on a 5-point Likert-type scale. |
Countries
Denmark
Contacts
Primary ContactSilvia Lo Vecchio
Outcome results
None listed