Figure 6.

Cilostamide (Cil) and rolipram (Rol), administered together, potentiate the chronotropic effects of (−)-adrenaline (a) and uncover β₂AR-mediated inotropic effects in the presence of CGP20712A, sensitive to blockade by ICI118551, in left atrium (b) but not in right ventricle (c). Data from left atria in the presence of CGP20712A were fitted for two β-adrenoceptor populations with −log EC₅₀ M of 7.93±0.30 (β₂-adrenoceptor) and 5.53±0.16 (β₁-adrenoceptor) and fractional E_max of 0.74±0.07 (β₁-adrenoceptor) and 0.26±0.07 (β₂-adrenoceptor). The left atrial −log EC₅₀ M of the curve for (−)-adrenaline in the presence of both CGP20712A and ICI118551 was 5.44±0.08.