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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
26
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.
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.
Aalborg University
Aalborg, Aalborg, Denmark
RECRUITINGAssessment 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'.
Time frame: 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'
Time frame: 1 minute after every itch inductions
Microvascular reactivity
The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging.
Time frame: 10 minutes after every itch inductions
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 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").
Time frame: 15 minutes after every itch inductions
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