Neuronal sensitization for histamine-induced itch in lesional skin of patients with atopic dermatitis.
OBJECTIVE
Lowered threshold of neurons (ie, neuronal sensitization) in atopic dermatitis was investigated by testing sensitivity to histamine.


METHODS
Comparative study.


METHODS
A dermatological clinic and a research laboratory.


METHODS
Eighteen patients with atopic dermatitis (AD) and 6 patients with chronic plaque-type psoriasis as well as 14 healthy control subjects.


METHODS
Histamine prick was performed in lesional and nonlesional skin of patients and in control subjects.


METHODS
Axon reflex flare and wheal were measured planimetrically, and the itch intensity was rated on a numerical scale (0-10).


RESULTS
In nonlesional skin of patients with AD, itch intensity and axon reflex flare were both significantly smaller compared with controls (mean +/- SEM maximum itch, 1.5 +/- 0.3 vs 3.1 +/- 0.2 [P<.05]; mean +/- SEM diameter, 12.3 +/- 2.0 vs 25.3 +/- 2.5 mm [P<.01]). In lesional skin of patients with AD, on the contrary, massive itch was provoked (maximum itch, 4.4 +/- 0.3), although flare was relatively small (diameter, 16.1 +/- 3.4 mm). Itch ratings in patients with psoriasis were low both in lesional and nonlesional skin (maximum itch, 1.3 +/- 0.6 and 1.0 +/- 0.4, respectively).


CONCLUSIONS
As the area of axon reflex flare is an indirect measure of activity in primary afferent neurons, our results suggest a decreased activation of peripheral pruriceptors in patients with AD. The massively increased itch in lesional skin of patients with AD might therefore be based on sensitization for itch in the spinal cord rather than in primary afferent neurons. This sensitization does not appear to be simply based on skin inflammation because histamine-induced itch was not augmented in lesional skin of psoriasis.
Ikoma
Akihiko
A
Departments of Dermatology, Kyoto University, Kyoto, Japan.
Rukwied
Roman
R
Ständer
Sonja
S
Steinhoff
Martin
M
Miyachi
Yoshiki
Y
Schmelz
Martin
M
D000328:Adult; D001369:Axons; D016022:Case-Control Studies; D002490:Central Nervous System / Q000503:physiopathology; D003876:Dermatitis, Atopic / Q000503:physiopathology*; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009474:Neurons; D011537:Pruritus; D011565:Psoriasis / Q000503:physiopathology; D012018:Reflex; D012684:Sensory Thresholds; D012867:Skin / Q000187:drug effects / Q000294:innervation* / Q000503:physiopathology*; D012882:Skin Tests
D006632:Histamine