The resulting MR images showed that
active scratching more effectively relieved itch than did passive scratching,
as reflected in more extensive deactivation of the anterior cingulated cortex,
prefrontal cortex, insult, and lent form nucleus. Involvement of the reward
system was reflected in deactivation of the ventral tegument from the brain and
the rape nucleus by active scratching in comparison to itching.
In contrast, passive scratching was
associated with deactivation of the anterior cingulated cortex, the medial orbit
frontal cortex, caudate nucleus, and the nucleus accumbency.
"Current experimental
approaches to investigate the pathogenesis of chronic prorates are largely
limited to rodent models," Netkeeper and colleagues stated in a poster
presentation. "This is the first study to show that the itch-specific
receptor GRPR and its legend GRP are linked to chronic itch in primates."
A third report at the SID meeting provided details of a clinical investigation into variations in itch perception and the relief afforded by scratching. After induction of itching by cowage exposure, 18 volunteers rated itch intensity and the pleasurably of scratching using a visual analog scale. The forearm, ankle, and back were tested separately.
