Reversibility of baroreceptor hyposensitivity during reversal of hypertension.
The extent and characteristics of reversal of baroreceptor resetting after pressure normalization were studied in rats with renal hypertension of 2 months' duration. During the control period, the displacement of the entire baroreceptor function curve was accompanied by a decrease slope, indicating that the gain sensitivity was depressed by 36% in the renal hypertensive rats. In response to changes of +10 and -10 mm Hg in the control pressure, the gain sensitivity was attenuated by 56% and 42%, respectively. Two minutes after unclipping and bleeding when necessary, mean arterial pressure decreased from 171 +/- 11 to 134 +/- 11 mm Hg and remained at approximately the same level for the 2-hour period of observation. The extent of reversal of the mean pressure threshold for activation of the baroreceptors was approximately constant (approximately 60%) in the time range of 2-120 minutes. The extent of reversal was slightly higher when the changes in systolic pressure threshold divided by the total change in control diastolic pressure were calculated (maximal of 83%). During the first 20 minutes, the displacements of the curves were parallel with no change in the depressed gain sensitivity. Complete normalization of gain sensitivity was observed after 90-120 minutes. The data indicate that, within the first 2 hours of pressure normalization of chronic renal hypertensive rats, 1) reversal of the resetting of pressure threshold is pronounced (60-80%) but still incomplete and 2) gain sensitivity returns completely to normal.
Moreira
E D
ED
Heart Institute, Faculty of Medicine, University of Sao Paulo, Brazil.
Ida
F
F
Krieger
E M
EM
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D004056:Differential Threshold; D006977:Hypertension, Renal / Q000503:physiopathology*; D011311:Pressoreceptors / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains