Different effects of prostaglandins on adrenergic neurotransmission in atrial and ventricular preparations.

1. The effects of prostaglandin E2 (PGE2) and iloprost on the cardiac response to adrenergic nerve stimulation in guinea-pig atrial and ventricular preparations have been studied. 2. In guinea-pig isolated atria both PGE2 (0.1-10 nM) and iloprost (0.1-3 microM) concentration-dependently reduced the cardiac response to adrenergic nerve stimulation. 3. The inhibition of cyclo-oxygenase by indomethacin and acetylsalicylic acid potentiated the response to nerve stimulation in the atrial preparations. 4. Arachidonic acid (1-10 microM) reduced the response to nerve stimulation in atria. This effect was prevented by indomethacin and acetylsalicylic acid. 5. In guinea-pig ventricles PGE2 and iloprost were found to be effective at higher concentrations than in atrial preparations: arachidonic acid, indomethacin or acetylsalicylic acid did not modify the cardiac response to adrenergic nerve stimulation. 6. These results suggest a different modulator role for endogenous prostaglandins in atrial and ventricular tissue.