The reflex interaction of cyclic AMP (DBcAMP) on arterial pressure

SUMMARYDibutiryl cyclic adenosine monophosphate (DBcAMP) is a derivative of cAMP, asecond messenger. The difference between cAMP is its easy penetration into the cell.Therefore, DBcAMP is expected to show similar effects as cAMP. Indeed, DBcAMP causessignificant decreases in mean arterial blood and this decrease is generally attributed to itsvasodilatative effect. The decreasing effect in mean arterial blood pressure and heart rate ofDBcAMP occurs in the presence of normal vagal tone. The fact that this decrease is not dosedependent suggests that this may be reflex response. In the present study, we have examinedthe blood pressure and heart rate following DBcAMP administration and left unilateralcervical vagotomy to reveal the role of parasympathetic interactions in this reflex response.We used Sprague-Dawley rats weighing 250-280 g in the experiment. Once the dose-response curve of DBcAMP is established, four groups are formed (n=28). First group(control group) received 1 mL saline bolus through the femoral artery. Second group had 15mg/kg DBcAMP in 1 mL saline. Third group underwent left vagotomy. Fourth group had15 mg/kg DBcAMP and had left cervical vagotomy 3 minutes afterwards. Mean arterialpressure (MAP) and heart rate (HR) were measured continuously for an hour on each animaland recorded digitally.We have shown that decreases in HR and MAP secondary to DBcAMP were not dosedependent. Therefore involvement of complex reflex mechanisms has been implicated.DBcAMP in conjunction with vagotomy resulted in more pronounced decrease in HR, i.e.potentiation. The similarity in MAP suggests that vagotomy could not neutralize the effects ofDBcAMP. As a result cardiovascular depressive effects of DBcAMP, especially on the MAPlevel, occurs through other regulators or secondary messengers other than vagal reflexes.