A Mechanistic Evaluation of the Interactions Between Thermoceptive and Pruriceptive Sensory Processing

Study Overview
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Brief Summary
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The purpose of this human experimental study is to evaluate the pattern of itch intensity over time in response to strong, short-term heat stimulation in two different models of histamine and cowhage-induced itch. Moreover, the purpose is to evaluate the effect of mild pre-heating of the skin in human experimental models of histamine, cowhage and serotonin. Finally, we want to investigate the effect of short-term intense heat stimulation on previously anesthetized skin.

Official Title
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En Mekanistisk undersøgelse af Interaktioner Imellem Det Thermoceptive og Det Pruriceptive Sensoriske System

Conditions
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Itch, Thermal Stimulation, Histamine, Cowhage, Serotonine

Intervention / Treatment
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* Drug: Lidocaine
* Other: Histamine
* Other: Cowhage
* Other: Heat stimulation
* Other: Pre-heating
* Other: Serotonin


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy men and women Age 18-60 years Able to speak and understand English Exclusion Criteria: Suffering from chronic disease Pregnancy or lactation Prior experience of adverse effects from anaesthetic, specifically Lidocaine Drug addiction defined as the use of cannabis, opioids or other drugs - 5 - Previous neurologic, musculoskeletal or mental illnesses Lack of ability to cooperate Current use of medications that may affect the trial Active skin diseases Active participation in other experiments currently ongoing or within the last 14 days Tattoos on volar forearms that will interfere with local skin measurements

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 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
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Histamine+cowhage+heat<br> | Other: Histamine<br>* Skin Prick Test with Histamine<br>Other: Cowhage<br>* Manually skin insertion of cowhage spicules<br>Other: Heat stimulation<br>* Short heat stimulation<br>|
| Experimental: Histamine+cowhage+serotonin+pre-heating<br> | Other: Histamine<br>* Skin Prick Test with Histamine<br>Other: Cowhage<br>* Manually skin insertion of cowhage spicules<br>Other: Pre-heating<br>* Mild skin pre-heating<br>Other: Serotonin<br>* Serotonin electrophoresis<br>|
| Placebo Comparator: lidocaine and saline+heat<br> | Drug: Lidocaine<br>* Lidocaine intradermal injection<br>Other: Heat stimulation<br>* Short heat stimulation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| eVAS Itch | Electronic Visual Analog Scale for itch sensation. 0-100 scale, it measures the self-estimated itch the subject experience on a scale where 0 correspond to No itch and 100 Worst itch imaginable. | 10 minutes | 
| Skin temperature | Infrared skin thermometer | 5 seconds | 
| eVAS Pain | Electronic Visual Analog Scale for pain sensation. 0-100 scale, it measures the self-estimated pain the subject experience on a scale where 0 correspond to No pain and 100 Worst pain imaginable. | 10 minutes |