Activation of a bradykinin receptor in peripheral nerve and spinal cord in the neonatal rat in vitro.

In an in vitro preparation of the neonatal rat spinal cord with attached tail, administration of bradykinin (Bk) to the spinal cord or to the tail produced depolarization of a ventral root (L3-L5). The effect of Bk at each site was selectively and reversibly antagonized by D-Arg [Hyp2, Thi5,8 D-Phe7]-Bk but could not be mimicked or antagonized by the B1-receptor ligands [des-Arg9]-Bk or Leu8[des-Arg9]-Bk, respectively. Peripherally evoked noxious responses produced by capsaicin or heat, were unaffected by either antagonist administered to the spinal cord. These data suggest that Bk-evoked responses in the spinal cord and at peripheral nociceptors were mediated via a receptor which by definition is of the B2-type. Additionally Bk is unlikely to be a physiological mediator of acute nociception in the spinal cord.