1. Pentolinium tartrate (a ganglionic blocker) was injected in conscious rats during the early and late phases of two-kidney renal hypertension produced by aortic ligation.
2. In the early phase (5 days after aortic ligation), ganglionic blockade resulted in a decrease in blood pressure equal to that obtained in normotensive rats. Later, at days 12 and 40, for equally severe hypertension, ganglion blockade resulted in a greater decrease in blood pressure.
3. A 30 min infusion of [Sar1, Ala8]angiotensin II during the pentolinium-induced nadir in blood pressure resulted in a further decrease in blood pressure at day 5. Later, at days 12 and 40, this effect was smaller.
4. A 300 min infusion of [Sar1, Ala8]angiotensin II normalized the blood pressure in hypertensive rats at day 40. This delayed response may be secondary to a central effect of the antagonist, reducing neurogenic tone or peripheral antagonism of locally generated angiotensin II in the blood vessel walls.
5. At day 40, removal of the small left kidney resulted in a greater decrease in blood pressure. This suggests the presence of a renal factor other than renin in the chronic phase of this hypertension.