Bradykinin activates peripheral capsaicin-sensitive fibres via a second messenger system

A preparation of the neonatal rat spinal cord with attached tail was maintained in vitro and was used to study the mechanism of action of bradykinin on peripheral nociceptors. Spinal ventral root depolarization was used as an index of peripheral fibre activation. Capsaicin-sensitive fibres in the tail were activated by bradykinin and a phorbol ester. The protein kinase C inhibitor staurosporine attenuated the effect of bradykinin and phorbol. [Des-Arg9]-bradykinin was inactive but bradykinin responses were reversibly antagonized by D-Arg0-Hyp2-Thi5,8-D Phe7-bradykinin. These data suggest that bradykinin activates nociceptors via a bradykinin B2-receptor coupled to protein kinase C.