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In This experiment, the investigators would like to design a new itch model based on the temporal summation of pruritic stimuli. The hypothesis behind this study (temporal summation) is that two overlapped applications of pruritogens will result in a higher itch sensation compared with a single application.
Chronic itch affects approximately a fifth of the global population and is associated with substantial negative consequences for the affected individuals. Furthermore, there is a lack of efficient treatment options for chronic itch. In order to mimic a clinical itch condition as presented in patients, the aim of the project is to investigate a new itch model based on the multiple applications of pruritogens (temporal summation). In particular, the purpose is to evaluate if a single application of cowhage/histamine (non-histaminergic and histaminergic itch, respectively) results in a lower itch sensation compared with two overlapped applications of the pruritogens on the same area.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 1st pruritogen | Experimental | The subproject is conducted in 1 session (approx. 3 hours in total) divided into two parts. In the first part, 3 test areas (3x3 cm) will be selected on one forearm of the subject. The 3 areas will be randomly treated with 1 application of cowhage, 2 applications of cowhage (the second application will be conducted 90 seconds after the first one in the same area), and 2 applications of cowhage (the second application will be conducted 180 seconds after the first one in the same area). Itch will be monitored using a VAS (visual analog scale) for 15 min in each session. After the removal of cowhage, FLPI, alloknesis, and mechanically evoked itch will be measured. |
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| 2nd pruritogen | Experimental | The second part will be conducted 20 minutes after the first part, and the procedure will be the same, but using histamine instead of cowhage. The two parts will be randomized between subjects. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Histamine | Other | Histaminergic itch will be evoked by a 1% histamine solution. A droplet of histamine solution will be placed on the predetermined area on the forearm, and the SPT lancet will be pierced through the histamine. |
| Measure | Description | Time Frame |
|---|---|---|
| Assessment of itch | Immediately following the itch provocations, participants will be instructed to rate the itch intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no itch' and 100 'worst itch imaginable'. | 1 minute after every itch inductions |
| Assessment of pain | Immediately following the itch provocations, participants will be instructed to rate the pain intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no pain' and 100 'worst pain imaginable' | 1 minute after every itch inductions |
| Measure | Description | Time Frame |
|---|---|---|
| Microvascular reactivity | The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging. | 10 minutes after every itch inductions |
| Alloknesis |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Silvia Lo Vecchio, PhD | Contact | +4521397785 | slv@hst.aau.dk | |
| Giulia Erica Aliotta, PhD | Contact | 50290580 | gea@hst.aau.dk |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Aalborg University | Recruiting | Aalborg | Aalborg | 9260 | Denmark |
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| ID | Term |
|---|---|
| D006632 | Histamine |
| ID | Term |
|---|---|
| D015306 | Biogenic Monoamines |
| D001679 | Biogenic Amines |
| D000588 | Amines |
| D009930 | Organic Chemicals |
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The participants will randomly receive applications of cowhage and histamine
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Participant will be blinded about application of pruritogens
| Cowhage | Other | 25 spicules will be inserted in the center of the predefined skin area on the mandibular area. The spicules will be gently rubbed for 15-20 seconds in circular motion to facilitate epidermal penetration. |
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Alloknesis sensation is measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN.
| 12 minutes after every itch inductions |
| Mechanically evoked itch | Mechanically evoked itch is measured using three von Frey filaments of 4.08, 4.16 and 4.31 (1.0, 1.4, 2.0 g, respectively) (North Coast Medical, Gilroy, CA). The center of the skin area is stimulated by 3 pricks, repeated 3 times in short succession. After a total of 9 stimulations, the participants will report the itch elicited on a numerical rating scale (NRS) from 0 to 10 (0 = "no itch"; 10 = "worst imaginable itch"). | 15 minutes after every itch inductions |
| D005021 |
| Ethylamines |
| D007093 | Imidazoles |
| D001393 | Azoles |
| D006573 | Heterocyclic Compounds, 1-Ring |
| D006571 | Heterocyclic Compounds |
| D012898 | Autacoids |
| D018836 | Inflammation Mediators |
| D001685 | Biological Factors |