Baroreceptor sensitivity during the compensatory phase of left ventricular overloading.
This study focused on the role of the baroreceptor-mediated control during the compensatory process after acute left ventricular overloading induced by aortic regurgitation (AR). Baroreceptor-heart rate sensitivity was measured using a phenylephrine-induced increase in blood pressure according to the steady state method before, 1 day, 1 week and 4 weeks after production of AR in 7 rabbits, and compared with 6 other rabbits that underwent a sham operation. Blood pressure was monitored noninvasively using Finapres in the unanesthetized state. Four weeks after the procedure, the left ventricular diameters of both end-diastole and end-systole were larger in the rabbits with AR than in the sham-operated rabbits. There was no difference in the left ventricular end-diastolic pressure or cardiac output. Left ventricular weight was higher in the rabbits with AR than in the sham-operated rabbits. Myocardial beta-adrenergic receptor density and norepinephrine content were comparable between the two groups. Baroreceptor-heart rate sensitivity significantly decreased 1 week after production of AR, and this alteration in sensitivity was partially restored 4 weeks after production of AR. These findings suggested that the altered baroreceptor-heart rate sensitivity was reversible, relating to the compensatory process after acute left ventricular overloading, and that these changes had some role in its pathophysiology.
Nishimura
H
H
Department of Medicine, Keio University School of Medicine, Tokyo, Japan.
Yoshikawa
T
T
Anzai
T
T
Baba
A
A
Kobayashi
N
N
Wainai
Y
Y
Ogawa
S
S
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001022:Aortic Valve Insufficiency / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology*; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D016277:Ventricular Function, Left
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine