Fig. 9. Inhibition of FRET ratio and CBF increases with H89 and Rp-8-Br-cAMPS. Non-permeabilized cells were perfused basolaterally with 400 µM Rp-8-Br-cAMPS (inhibitor of RII), or 10 µM H89 (inhibitor of CAT) in the presence of 1 µM, 10 µM or 20 µM forskolin. (A) FRET ratios. Forskolin-mediated dissociation of PKA subunits is prevented by Rp-8-Br-cAMPS (inhibitor of RII), whereas H89 (inhibitor of CAT) did not prevent forskolin-induced PKA subunit dissociation. (B) CBF. H-89 significantly blocks CBF increases, whereas Rp-8-Br-cAMPS allows CBF increases to only 15% above baseline at all forskolin concentrations tested. This partial effect of Rp-Br-cAMPS is likely due to an estimated 70% inhibition of PKA dissociation at the used concentration; the remaining activation of PKA cannot be discerned with FRET but still activates CBF to a certain degree. *P<0.05, comparing groups indicated by brackets.