Fig. 2.
FRET-based cAMP sensors are suitable to monitor cAMP decreases in living cells induced by activation of Gi/o-coupled α2A receptors. FRET measurements with HEK293 cells expressing Gi/o-protein-coupled α2A receptors together with one of the indicated FRET-based cAMP sensors. a–e Representative FRET measurements are displayed showing time courses of the normalized yellow and cyan fluorescence signals (left) and of the normalized FRET signal (right). Black bars indicate application of the adenylyl cyclase activator forskolin (FSK) in submaximal concentration (1 μM) to increase basal cAMP levels. Gray bars show application of the selective α2A receptor agonist guanfacine (250 μM). f Summary of FRET signal increases induced by guanfacine in the presence (hatched bars) or absence (solid bars) of the selective α2A receptor antagonist yohimbine (1 mM). Numbers over bars indicate the numbers of measured cells and the number of individual coverslips from at least 3 experimental days. Significances tested between cells treated and not treated with yohimbine. *P < 0.05, **P < 0.01