BRADYKININ-RESPONSIVE CELLS OF DORSAL-ROOT GANGLIA IN CULTURE - CELL-SIZE, FIRING, CYTOSOLIC CALCIUM, AND SUBSTANCE-P

1. We analyze bradykinin-sensitive cells of the mouse dorsal root ganglion in culture from the viewpoints of cell size, electrical responses, and Ca2+ concentration change due to bradykinin and immunocytochemistry of substance P. 2. Sixteen percent of cells in the cell group 26-30 mu m in diameter fired in response to 10 mu M bradykinin. None of other cell groups showed a firing response to bradykinin. 3. We measured a cytosolic Ca2+ change due to bradykinin using a Ca2+-sensitive fluorescent dye, Fura 2. Tile rapid rise (peak time, 20 sec) in the Ca2+ concentration was ascribed to Ca2+ release from intracellular Ca2+ stores. The profound change in the Ca2+ concentration was observed again in the cell group 26-30 mu m in diameter. Seventeen percent of cells in this group increased the Ca2+ concentration by approximately seven times that at resting level. 4. Among cells which increase Ca2+ concentration responding to bradykinin, 83% of them contain substance P (an immunocytochemical study). 5. We conclude that 16-17% of the cell group 26-30 mu m in diameter of the dorsal root ganglia in culture are polymodal nociceptors and respond to bradykinin.