Role of histamine H₁ receptor in pain perception: A study of the receptor gene knockout mice

To study the participation of histamine H₁ receptors in pain perception, histamine H₁ receptor knockout mice were examined for pain threshold by means of three different kinds of nociceptive tasks. These included assays for thermal nociception (hot-plate, tail-flick, paw-withdrawal), mechanical nociception (tail-pressure), and chemical nociception (abdominal constriction, formalin test, capsaicin test) which evoked pain by the activation in nociceptive Aδ and C fibers. The mutant mice lacking histamine H₁ receptors showed significantly fewer nociceptive responses to the hot-plate, tail-flick, tail-pressure, paw-withdrawal, formalin, capsaicin, and abdominal constriction tests. Sensitivity to noxious stimuli in histamine H₁ receptor knockout mice significantly decreased when compared to wild-type mice. This data indicates that histamine plays an important role in both somatic and visceral pain perceptions through histamine H₁ receptors. The difference in the effect of histamine H₁ receptors antagonist, the active (D-) and inactive (L-) isomers of chlorpheniramine on ICR mice further substantiates the evidence of the role of histamine H₁ receptors on pain threshold. Copyright (C) 2000 Elsevier Science B.V.