M-CURRENT SUPPRESSION IN PC12 CELLS BY BRADYKININ IS MEDIATED BY A PERTUSSIS TOXIN-INSENSITIVE G-PROTEIN AND MODULATED BY INTRACELLULAR CALCIUM

Inhibition of the hi-current in PC12 cells by bradykinin has been stud ied under whole-cell recording conditions. In cells dialyzed with GTP- gamma-S, bradykinin produced a total and irreversible hi-current suppr ession, while the inhibition was attenuated in cells dialyzed with GDP -beta-S. Inhibition occurred in cells pretreated with pertussis toxin, while this treatment prevented the modulation of Ca2+ currents by mus carine. The rate and extent of inhibition increased with the level of intracellular Ca2+ from 0 to 70 nM. These results indicate that a pert ussis toxin insensitive G-protein mediates the action of bradykinin on the hi-current, and some steps in the second messenger cascade are mo dulated by Ca2+.