To clarify the mechanisms by which compound 48/80 (C48/80) induces scratching behavior, the involvement of dopamine D(1) receptors was investigated. The intracisternal (i.t.) administration of SCH23390 (1.0 μg), a selective dopamine D(1) receptor antagonist, significantly decreased C48/80-induced scratching behavior in mice. These results suggest that dopamine D(1) receptors contribute to scratching behavior or the itch sensation induced by subcutaneous injection of C48/80 in mice. Co-administration of SCH23390 and C48/80 enhanced c-fos immunoreactivities in the peduncular part of the lateral hypothalamus (PLH), whereas the immunoreactivities in the other groups were unchanged. The dopaminergic system may be playing an important role in the suppression of C48/80-induced scratching behavior by SCH23390.
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