Effect of desipramine on spontaneous arterial pressure oscillations in the rat

There has been no previous report on the effect of the noradrenaline uptake inhibitor desipramine on short-term variability of arterial pressure. Mean arterial pressure was recorded in 9 conscious resting rats during 4 consecutive 30-min periods: (1) under baseline conditions, (2) after desipramine administration (2 mg/kg i.v., followed by 1 mg/kg every hour), then after (3) cardiac autonomic blockade with methylatropine and atenolol, and (4) alpha-adrenoceptor blockade with phentolamine. Fast Fourier transform analysis was applied to beat-to-beat data after resampling at 10 Hz of consecutive 205-s time series. Desipramine did not change the mean level and overall variability of mean arterial pressure. However, spectral power in the mid-frequency (0.3-0.5 Hz) band containing the Mayer waves was reduced by more than 80%, and power in the low-frequency (0.05-0.2 Hz) band was enhanced by approximately 50%, especially due to the appearance of a major oscillation centred at 0.095 +/- 0.005 Hz. This slow oscillation was further enhanced after cardiac autonomic blockade and was abolished after alpha-adrenoceptor blockade. In conclusion, desipramine profoundly alters short-term arterial pressure variability in resting rats, mainly by shifting vasomotor waves from 0.4 to 0.1 Hz. Desipramine may prove a valuable pharmacological tool to study the dynamic aspects of arterial pressure control.