Effects of the Phosphodiesterase Inhibitor Enoximone on the Autonomic Innervation of the Isolated Heart

Enoximone is a selective inhibitor of a low Km, cyclic AMP-specific type of phosphodiesterase (PDE III). In guinea pig and chicken atria, enoximone (0.1-100 mumol/L) caused a weak increase in the force of contraction. The heart rate was slightly enhanced or was unchanged (chicken). Enoximone (30 mumol/L) also failed to shift the concentration-response curves for the positive inotropic and chronotropic effects of norepinephrine in guinea pig atria. Under almost the same conditions, enoximone and the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) markedly potentiated the forskolin-induced mobilization of choline from phospholipids. The concentrations of IBMX (100 mumol/L) and o…

Der Einflu� von Atropin auf die Noradrenalin-Freisetzung durch Acetylcholin

Chapter 19 Muscarinic activation of phosphatidylcholine hydrolysis

Publisher Summary This chapter focuses on the muscarinic activation of phosphatidylcholine hydrolysis. The release of choline from tissues or cells is a sensitive indicator of an enhanced hydrolysis of phosphatidylcholine (PtdCho) and is easily determined by chemiluminescence. In certain cells, choline release may reflect the activity of a specific receptor-activated enzyme catalyzing PtdCho hydrolysis. A physiological role of the receptor-mediated release of choline in the brain is given by its role as biosynthetic precursor for acetylcholine (ACh) and phospholipids. When PtdCho hydrolysis is investigated to identify the phospholipase involved, the sole determination of enzymatic products …