Humanizing mice: catching up with elusive B1 receptors.

Bradykinin receptor activation plays an important role in pain arising following tissue inflammation, and recent studies have suggested that bradykinin B1 receptors in particular may be important in chronic pain related to arthritis and various neuropathies. The investigation of the function of the B1 receptors in vivo has been hampered by the lack of nonpeptide antagonists, and the development of such compounds made more difficult by the considerable species variation between human and rodent B1 receptors. In this issue, Fox and co-workers report the creation of a mouse that has had the human B1 gene inserted into the corresponding mouse locus, and they exploit this animal to study the effects of a novel, nonpeptide B1 receptor antagonist on measures of acute nociception and nociception following inflammation. By creating a platform that allows the study of human B1 receptors in vivo, these investigators have provided a tool to significantly advance the understanding of the kallikrein-kinin system in physiological and pathophysiological states.