Blood pressure control in pithed rat

In the pithed Wistar rats Captopril (2 mg/kg) decreased the mean arterial pressure (MAP) 21%. Further injection of a specific antagonist decreased the vasoconstrictor action of vasopressin (aAVP, 10 micrograms/kg) an additional 6%. Reversal in the order of drug administration did not change these percentages. The osmotic stimulus evoked by the infusion of hypertonic saline (ClNa 9%, 0.018 ml/min, 2 hr) significantly increased MAP, this increase being almost totally reversed by the aAVP (10 micrograms/kg). These findings suggest a greater role of the renin-angiotensin system than of the vasopressin (AVP) in the maintenance of MAP in the pithed rat; AVP, moreover, can be released by means of an osmotic stimulus.