Evidence that protein kinase C activation is involved in the excitatory and facilitatory effects of bradykinin on canine visceral nociceptors in vitro

The involvement of protein kinase (PK) C activation in the effects of bradykinin (BK) on peripheral nociceptors, polymodal receptors, was examined using canine testis-spermatic nerve preparations in vitro. Phorbol 12,13-dibutyrate 0.1 mu M, which activates PKC, suppressed the BK-induced excitation when applied for 3-5 min prior to BK application, but facilitated it when applied simultaneously with BK. Neither effect was induced by an inactive phorbol ester, 4 alpha-phorbol 12, 13-didecanoate, demonstrating that both effects were mediated through the activation of PKC. In addition, staurosporine 1 mu M, a PK inhibitor, suppressed both BK-induced excitation and facilitation of the heat response of testicular polymodal receptors without influencing on-going activities and the heat response itself. These results suggest that PKC activation is involved in the excitatory and facilitatory effects of BK on peripheral nociceptors. (C) 1997 Elsevier Science Ireland Ltd.