Effects of dynorphin1-13 on cardiac rhythm and cyclic adenosine monophosphate (cAMP) levels in the isolated perfused rat heart.

We have studied the effects of dynorphin1-13 on cardiac rhythm and cAMP levels in the isolated perfused rat heart. The standard Langendorff isolated heart preparation was used. The myocardial cAMP levels and the incidence of cardiac arrhythmias were determined after injection of dynorphin1-13. Dynorphin1-13 caused simultaneously cardiac arrhythmias and an increase in myocardial cAMP levels in a dose-dependent manner, and both effects were antagonized by naloxone. Further studies are needed to determine whether myocardial cAMP mediates the dynorphin-induced cardiac arrhythmias.