Localization of B1 bradykinin receptor mRNA in the primate brain and spinal cord:: An in situ hybridization study

The bradykinin 1 and 2 receptors (B1R, B2R) are important mediators of cardiovascular homeostasis, inflammation, and nociception. While B2R is constitutively expressed in many tissues, B1R expression is thought to be absent, but induced under proinflammatory conditions. However, recent data from knockout mice have indicated that B1R acts centrally to mediate nociception, a finding that suggests the constitutive presence of B1R in brain and/or spinal cord. The purpose of the present study was to further elucidate the physiological role of B1R by evaluating the localization of B1R mRNA in the nonhuman primate brain and spinal cord with in situ hybridization. Cryostat sections from monkey brain and spinal cord were hybridized with a [S-35]-labeled riboprobe complementary to B1R mRNA, stringently washed, and apposed to film and emulsion. The results of these studies revealed the presence of B1R mRNA throughout the rostral-caudal extent of the brain and spinal cord. In particular, labeled cells were seen in the cerebral and entorhinal cortex, dentate gyrus, and pyramidal neurons of the hippocampus, in the thalamus, hypothalamus, amygdala, pontine nuclei, spinal cord, and dorsal root ganglion. Together the present findings offer detailed information about the distribution of B1R mRNA in the primate brain and spinal cord and demonstrate a basal level of expression in the primate nervous system. Moreover, these data provide a foundation for understanding the central actions of kinins and their putative role in mediating a number of processes, including pain and nociception. (C) 2003 Wiley-Liss, Inc.