Inverse relationship between heart rate and blood pressure variabilities in rats.

Author:

Ferrari A U1,Daffonchio A1,Albergati F1,Mancia G1

Affiliation:

1. Centro di Fisiologia Clinica e Ipertensione, Ospedale Maggiore, Milano, Italy.

Abstract

The interplay of heart rate variability, baroreceptor control of heart rate, and blood pressure (BP) variability was examined in chronically instrumented, unanesthetized, freely moving rats in which the efferent neural influences on heart rate were pharmacologically altered. In each rat, BP was recorded continuously for 90 minutes in the control condition and in one or more of the following conditions: 1) beta-adrenergic receptor blockade by propranolol, 1 mg/kg; 2) cholinergic blockade by atropine, 0.75 mg/kg, and 3) combined blockade by propranolol plus atropine. Each BP recording was analyzed beat-to-beat by a computer that calculated heart rate and BP variabilities, both expressed as variation coefficients. In addition, under each condition the sensitivity of the arterial baroreceptor control of heart rate was assessed by measuring the reflex changes in pulse interval in response to BP changes induced by bolus i.v. injections of phenylephrine and nitroprusside. As compared with the control condition, 1) propranolol (n = 10) reduced heart rate variability by 23 +/- 4% (p less than 0.01), only slightly impaired baroreceptor reflex sensitivity, and did not significantly modify BP variability (+11 +/- 7%); 2) atropine (n = 11) reduced heart rate variability by 30 +/- 7% (p less than 0.01), drastically impaired baroreceptor reflex sensitivity, and increased BP variability (+40 +/- 8%, p less than 0.01); 3) combined blockade (n = 10) caused variability and baroreceptor reflex changes similar to those induced by atropine alone. Thus, heart rate variability depends on both vagal and sympathetic influences. However, only the former component affects BP variability, that is, it plays an antioscillatory role.(ABSTRACT TRUNCATED AT 250 WORDS)

Publisher

Ovid Technologies (Wolters Kluwer Health)

Subject

Internal Medicine

Reference3 articles.

1. Minute-to-minute covariations in cardiovascular activity in conscious dogs;Anderson DE;Am J Physiol,1979

2. Ramirez J Bertinieri G Belli G etal. Reflex control of blood pressure and heart rate by arterial baroreceptors and by cardiopulmonary receptors in the unanesthetized cat. J Hypertens 1985^:327-335

3. Sokolow M Werdegar D Kain HK Hineman AT. Relationship between level of blood pressure measured casually and by

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