HRH4 and Pruritus: Another TRPV1 antagonist, AMD9810, was found to block excitation of sensory neurons and dramatically reduce scratching bouts in a mouse acute itch model induced by subcutaneous injection of immepip into the nape of the neck, but this is not observed for TRPA1 antagonist HC030031, suggesting that TRPV1 is implicated in histamine H4 receptor-mediated itch signaling (167).