B2 bradykinin receptor immunoreactivity in rat brain

Bradykinin has long been known to exist in the central nervous system and has been hypothesized to mediate specific functions. Despite an increasing understanding of the functions of bradykinin, little is known about the cell types expressing the bradykinin receptor within the brain. The present investigation employed a monoclonal antibody directed against the 15-amino-acid portion of the C-terminal of the human bradykinin B2 receptor to establish the cellular distribution of bradykinin B2 receptor immunoreactivity in the rat brain. Bradykinin B2 receptor immunoreactivity was ubiquitously and selectively observed in neurons, including those within the olfactory bulb, cerebral cortex, hippocampus, basal forebrain, basal ganglia, thalamus, hypothalamus, cerebellum, and brainstem nuclei. Bradykinin B2 receptor immunoreactivity was also present in the circumventricular organs including choroid plexus, subfornical organ, median eminence, and area postrema. Double-labeling experiments colocalizing the bradykinin B2 receptor with the neuronal marker NeuN or the astrocytic marker glial fibrillary acidic protein revealed that virtually 100% of the bradykinin B2 receptor-immunoreactive positive cells were neurons. The widespread distribution of bradykinin B2 receptor immunoreactivity in neuronal compartments suggests a greater than previously appreciated role for this peptide in neuronal function. (C) 2000 Wiley-Liss, Inc.