Fig. 6. Agonist-induced oscillations in levels of Ca²⁺ and cAMP. (A) Single-cell cytosolic Ca²⁺ changes in response to 10 µM CCh showing either (i) sustained Ca²⁺ increase or (ii) regular Ca²⁺ oscillations. (B) Parallel experiments measuring cAMP signals in individual Epac-1-probe- and AC8-expressing cells with and without external Ca²⁺. 10 nM PGE₁ was present throughout the period of CCh application.