Cerebral Networks Linked to Itch-related Sensations Induced by Histamine and Capsaicin.
This functional magnetic resonance imaging (fMRI) study explored the central nervous processing of itch induced by histamine and capsaicin, delivered via inactivated cowhage spicules, and the influence of low-dose naltrexone. Scratch bouts were delivered at regular intervals after spicule insertion in order temporarily to suppress the itch. At the end of each trial the subjects rated their itch and scratch-related sensations. Stepwise multiple regression analyses were employed for identifying cerebral networks contributing to the intensities of "itching", "burning", "stinging", "pricking" and "itch relief by scratching". In the capsaicin experiments a network for "burning" was identified, which included the posterior insula, caudate and putamen. In the histamine experiments networks for "itching" and "itch relief" were found, which included operculum, hippocampus and amygdala. Naltrexone generally reduced fMRI activation and the correlations between fMRI signal and ratings. Furthermore, scratching was significantly less pleasant under naltrexone.
Department of Physiology and Pathophysiology, FAU Erlangen/Nuremberg, Universitaetsstr. 17, DE-91054 Erlangen, Germany.
Verena
V
Vierow
Clemens
C
Forster
Rebekka
R
Vogelgsang
Arnd
A
Dörfler
Herman O
HO
Handwerker
D000293:Adolescent; D000328:Adult; D000679:Amygdala / Q000503:physiopathology; D001931:Brain Mapping; D002211:Capsaicin / Q000494:pharmacology; D002421:Caudate Nucleus / Q000503:physiopathology; D002540:Cerebral Cortex / Q000503:physiopathology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D059907:Functional Neuroimaging; D006624:Hippocampus / Q000503:physiopathology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010292:Paresthesia / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D011537:Pruritus / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D011699:Putamen / Q000503:physiopathology; D011897:Random Allocation; D012677:Sensation / Q000187:drug effects*; D012879:Skin Physiological Phenomena / Q000187:drug effects; D055815:Young Adult
D009292:Narcotic Antagonists; D009271:Naltrexone; D006632:Histamine; D002211:Capsaicin