[Functional state of baroreceptors of the aortic arch in experimental hypertension]

The bioelectrical activity of the aortic nerve was studied in normal rabbits and in those with experimentally induced hypertension. Electroneurograms of the aortic nerve of rabbits with renal and coarctational (stenosis of the abdominal aorta) hypertension demonstrated the same burst-like activity synchronous with the systolic contractions of the heart that was noted in normotensive animals. The threshold of the transit of the burst-like activity of the aortic nerve into the uniform one in cases of acutely elevated arterial pressure (induced by injections of noradrenalin and angiotensin) and the threshold of the disappearance of the mentioned activity after an acute reduction of the arterial pressure (induced by injections of acetylcholine, tetra-ethylammonium or by acute bleeding) in rabbits with renal and coarctational hypertension are shifted upwards, as compared to those in normotensive rabbits. It is the more true of the former threshold. The depressor reaction to the administration of the ganglionic blocker -- tetra-ethyl-ammonium -- in renal hypertension during the initial 2 months of the disease remains unchanged, with the exception of the 4th and 8th weeks, when it is elevated. It is concluded that the baroreceptors of the aortic arch percept the chronically elevated arterial pressure as a normal one reacting adequately to its acute changes in either direction. Thanks to this the barorecptors of the aortic arch strive to maintain a high level of the arterial pressure and provide for a stabilization of hypertension.