In This experiment, the investigators would like to test following hypotheses: repetitive cutaneous administration of pruritogens will lead to a more robust and longer lasting itch sensation compared with a single application. The aim of this project is to investigate a new itch model based on repetitive administration of three different pruritogens: histamine (histaminergic itch), cowhage, and BAM 8-22 (non-histaminergic itch).
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 repetitive administration of three different pruritogens: histamine (histaminergic itch), cowhage, and BAM 8-22 (non-histaminergic itch). The hypothesis is that repetitive cutaneous administration of pruritogens will lead to a more robust and longer-lasting itch sensation compared with a single application. This proposal for a new itch model could better mimic clinical itch conditions and be used to investigate fundamental mechanisms, new anti-pruritic drugs, and their possible mechanisms of action.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
30
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 with 120 g of pressure for 1-2 seconds
25 spicules will be inserted in the centre 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
Aalborg University
Aalborg, Denmark, Denmark
Assessment of itch intensity
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'.
Time frame: 1 minute post itch provocation
Assessment of pain intensity
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'.
Time frame: 1 minute post itch provocation
Superficial blood perfusion
The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging.
Time frame: 10 minutes post itch provocation
Alloknesis
Alloknesis sensation is measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN.
Time frame: 12 minutes post itch provocation
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").
Time frame: 15 minutes post itch provocation
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