Testing Protocol to Efficiently Induce Itch

Study Overview
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Brief Summary
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This subproject aims to evaluate a new nerve excitability protocol to induce itch in healthy controls by electrical stimulation. Itch has many similarities with pain, and the nerve fibers that mediate the two sensations probably have the same morphological and excitability properties. The method used in this project will be the same as our research group uses for studying nociceptor fibers (PTT technique), but the focus is on the itch sensation. Since the itch fibers also terminate in the epidermis, our PTT technique should also be able to activate itch fibers, similar to pain fibers. If itch could be effectively induced by electrical stimulation, this would generate a valuable tool for studying itch in healthy controls. The sub-project takes place in 2 sessions (2 hours each).

Official Title
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Nerve Excitability Testing Protocol to Efficiently Induce Itch

Conditions
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Itch

Intervention / Treatment
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* Drug: Anti-histamine cream 1 hour
* Drug: Local anesthetic cream 1 hour


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy men and women in the age 18-80 years who speak and understand Exclusion Criteria: Pregnancy or breast feeding Drug addiction defined as the use of cannabis, opioids or other drugs Previous and present neurologic, musculoskeletal or mental illnesses (e.g., epilepsy, neuropathy, fibromyalgia and depression) Skin diseases Past history of conditions possibly leading to neuropathy Inability to cooperate Current use of medications that may affect the study, e.g., analgesics Previous traumatic experience of an electrical accident Consumption of alcohol or painkillers within the last 24 hours Participation in other pain studies throughout the study period Patients with cardiac diseases (e.g., pacemaker).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Study group<br> | Drug: Anti-histamine cream 1 hour<br>* At the start of session 1, one area of the middle forearms of the participant will be located (4x4cm). On the area, anti-histamine cream will be applied for approximately 1 hour.<br>Drug: Local anesthetic cream 1 hour<br>* At the start of session 2, one area of the middle forearms of the participant will be located (4x4cm). On the area, local anesthetic cream (2.5% lidocain/2.5 prilocaine) will be applied for approximately 1 hour.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Perception threshold for pulse shape 1 | The perception threshold will be estimated for the electrical stimuli with pulse shape 1. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 2 | The perception threshold will be estimated for the electrical stimuli with pulse shape 2. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 3 | The perception threshold will be estimated for the electrical stimuli with pulse shape 3. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 4 | The perception threshold will be estimated for the electrical stimuli with pulse shape 4. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 1 when antihistamine cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 1 when anti-histamine cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session one. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 2 when anti-histamine cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 2 when anti-histamine cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session one. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 3 when anti-histamine cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 3 when anti-histamine cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session one. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 4 when anti-histamine cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 4 when anti-histamine cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session one. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 1 when local anaesthetic cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 1 when local anaesthetic cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 2 when local anaesthetic cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 2 when local anaesthetic cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 3 when local anaesthetic cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 3 when local anaesthetic cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session two. The outcome measure takes approximately 5 minutes to estimate. | 
| Perception threshold for pulse shape 4 when local anaesthetic cream has been applied | The perception threshold will be estimated for the electrical stimuli with pulse shape 4 when local anaesthetic cream has been applied for approximately an hour. The perception threshold is defined as the transcutaneous electrical current needed for the participant to perceive the stimulus. The electrode will be placed on the arm. The perception threshold will be estimated by the method of limits and the psi method. | This outcome measurement will be estimated during session two. The outcome measure takes approximately 5 minutes to estimate. | 
| Sensation for pulse 1 | The investigator will ask the participant to rate the sensation of electrical stimulation with pulse 1 for the three different conditions. The conditions are: control (not active cream), antihistamine cream, and local anesthetic cream. The scale is 0-10 for the three sensations touch, itch, and pain. Zero means no sensation, and ten is the worst pain/touch/itch imaginable. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Sensation for pulse 2 | The investigator will ask the participant to rate the sensation of electrical stimulation with pulse 2 for the three different conditions. The conditions are: control (not active cream), antihistamine cream, and local anesthetic cream. The scale is 0-10 for the three sensations touch, itch, and pain. Zero means no sensation, and ten is the worst pain/touch/itch imaginable. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Sensation for pulse 3 | The investigator will ask the participant to rate the sensation of electrical stimulation with pulse 3 for the three different conditions. The conditions are: control (not active cream), antihistamine cream, and local anesthetic cream. The scale is 0-10 for the three sensations touch, itch, and pain. Zero means no sensation, and ten is the worst pain/touch/itch imaginable. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. | 
| Sensation for pulse 4 | The investigator will ask the participant to rate the sensation of electrical stimulation with pulse 4 for the three different conditions. The conditions are: control (not active cream), antihistamine cream, and local anesthetic cream. The scale is 0-10 for the three sensations touch, itch, and pain. Zero means no sensation, and ten is the worst pain/touch/itch imaginable. | This outcome measurement will be estimated during sessions one and two. The outcome measure takes approximately 5 minutes to estimate. |