Figure 4.

The influence of PDE inhibitors on the positive inotropic effects of (−)-noradrenaline through β₁-adrenoceptors and (−)-adrenaline through β₂-adrenoceptors of the free right ventricular wall. (A) Potentiation of the positive inotropic effects of (−)-noradrenaline by rolipram (Rol), concurrent cilostamide + rolipram and IBMX but not by cilostamide (Cil) alone. (B) Effects of (−)-adrenaline mediated through both β₁-adrenoceptors and β₂-adrenoceptors in the absence of antagonists (controls), through β₁-adrenoceptors in the presence of ICI118551 (ICI) and through β₂-adrenoceptors in the presence of CGP20712A (CGP). (C) Potentiation of the effects of (−)-adrenaline through β₂-adrenoceptors by cilostamide, concurrent cilostamide + rolipram and IBMX but not by rolipram. Fits of some biphasic curves were constrained by using the effect of (−)-isoprenaline as maximum. For further details see Figure 1.