Journal of Neuroscience, Vol 11, 1140-1149, Copyright © 1991 by Society for Neuroscience
Inhibition by bradykinin of voltage-activated barium current in a rat dorsal root ganglion cell line: role of protein kinase C
LM Boland, AC Allen and R Dingledine
Curriculum in Neurobiology, University of North Carolina, School of Medicine, Chapel Hill 27599-7365.
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.
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