Aortic Baroreceptor Activity during Permanent Distension of the Receptor Area

Aortic baroreceptor activity is known to be reduced in cases of persisting hypertension, the resetting probably resulting from changes in the aortic wall. The present investigation is an attempt to study the effects of permanent, localized dilatation of the aortic baroreceptor area on receptor activity. Ascending aortic stenosis was produced in 24 rabbits, and aortic diameters and aortic nerve activity were compared with results obtained in 10 normal rabbits. Aortograms four weeks after production of the stenosis showed diameters in the upper part of the ascending aorta and the aortic arch to be on average 16 % and 13 % greater than normal. Whereas an acute dilatation of this degree would have given marked increases of aortic nerve activity, the relationship between pressure and receptor activity was normal in animals with a permanent dilatation, both at pulsatile and steady pressures. The load‐length relationship of aortic strips from normal and dilated receptor area was also equal, indicating that the uniformity of the relationship between pressure and activity in the two situations, at least in steady states, was due to adaptation of the aortic wall. It thus seems that chronic increases of neither pressure nor receptor area diameter will have consequences for aortic baroreceptor activity.