Indirect actions of bradykinin on neonatal rat dorsal root ganglion neurones: a role for non-neuronal cells as nociceptors

1. In this study we have investigated the action of bradykinin (Bk) on cult ured neonatal rat dorsal root ganglion (DRG) cells, with the aim of elucida ting whether the neuronal response to Bk is influenced by association with non-neuronal satellite cells. 2. Bradykinin (100 nil) evoked an inward current (1(Bk)) in 51 of 58 voltag e clamped DRO neurones (holding potential (V-h) = -80 mV) that were in cont act with non-neuronal satellite cells. 3. Bradykinin failed to evoke an inward current in isolated DRG neurones (V -h = -80 mV) that were not, in contact with non-neuronal satellite cells (n = 41). 4. The lack of neuronal response to Bk was not influenced by time in cultur e. Bradykinin failed to evoke a response in isolated neurones through 1-5 d ays in culture. By contrast neurones in contact with satellite cells respon ded to Bk throughout the same time period. 5. Failure of isolated neurones to respond to Bk was not due to the replati ng procedure or to selective subcellular distribution of receptors/ion chan nels to the processes rather than the somata of neurones. 6. Using Indo-1 AM microfluorimetry Bk (100 nM) was demonstrated to evoke a n intracellular Ca2+ increase (Ca-Bk) in DRG neurones in contact with non-n euronal satellite cells and in isolated neurones. 7. These data suggest that the inward current response to Bk requires conta ct between DRG neurones and non-neuronal satellite cells. This implies an i ndirect mechanism of action for Bk via the non-neuronal cells, which may pe rform a nociceptive role. However, Bk can also act directly on the neurones , since it evokes Ca-Bk in isolated neurones. The relationship between Ca-B k and the Bk-induced inward current is unknown at present.