Inhibition by bradykinin of voltage-activated barium current in a rat dorsal root ganglion cell line: role of protein kinase C

The whole-cell patch-clamp technique was used to record Ba2+ currents through voltage-activated calcium channels in the clonal dorsal root ganglion cell line F11-B9. The pain-producing peptide bradykinin (BK; 100 nM) reduced the sustained Ba2+ current in F11-B9 cells by 30%. In cultures prelabeled with 3H-arachidonic acid and tested under ionic conditions similar to those used for recording Ba2+ currents, BK also induced a concentration-dependent, transient, 2.7-fold accumulation of 3H-diacylglycerol. Both the elevation of 3H-diacylglycerol and the inhibition of Ba2+ current began within 5 sec following BK exposure, and the effective concentration range of BK was similar for the 2 responses. In whole-cell recordings, extracellularly applied 1-oleoyl-2- acetylglycerol (OAG; 0.5–5 microM) mimicked the degree of block and occluded the block of sustained current by BK. Another protein kinase C (PKC) activator, 1,2-dioctanoylglycerol (diC8), blocked 70–100% of sustained current when applied intracellularly or extracellularly at 5 microM, whereas extracellular application of ethylene glycol dioctanoate (5 microM), an analog reported not to stimulate PKC, inhibited only 14% of sustained current. The pseudosubstrate peptide PKC19–36 (2 microM in pipette) and the lipid staurosporine (100 nM in pipette), both inhibitors of PKC, reduced the effects of maximal concentrations of OAG or BK by 55–60%. Dynorphin A applied intracellularly (2 microM) as a control for nonspecific effects of PKC19–36 did not inhibit the block of sustained current by BK. These data are consistent with the hypothesis that BK inhibits whole-cell sustained Ba2+ current in F11-B9 cells via a mechanism that involves activation of PKC.