Potentiation of the baroreceptor-heart rate reflex by sympathectomy in conscious rats.
- 1 August 1991
- journal article
- abstracts
- Published by Wolters Kluwer Health in Hypertension
- Vol. 18 (2), 230-235
- https://doi.org/10.1161/01.hyp.18.2.230
Abstract
In both animals and humans, stimuli leading to sympathetic activation are accompanied by an impairment of the baroreceptor-heart rate reflex. To determine whether sympathetic activity normally interferes with this reflex function we examined in conscious Wistar-Kyoto (WKY) rats the effect of chemical sympathectomy by 6-hydroxydopamine on the bradycardic response to baroreceptor stimulation induced by raising blood pressure via intravenous phenylephrine boluses; control rats received vehicle. Spontaneously hypertensive rats were also studied because in these animals there is both a baroreceptor reflex impairment and a sympathetic overactivity. Baroreceptor reflex sensitivity, calculated as the ratio of the peak increase in pulse interval to the peak increase in mean arterial pressure, was 75% greater in sympathectomized WKY rats than in control WKY rats (1.28 +/- 0.15 versus 0.73 +/- 0.10 msec/mm Hg, mean +/- SEM; p less than 0.01). The sympathectomy-induced increase in sensitivity was even larger in spontaneously hypertensive rats (SHR) (1.26 +/- 0.12 versus 0.44 +/- 0.06 msec/mm Hg in sympathectomized SHR versus control SHR, +186%; p less than 0.01) so that the impaired baroreceptor reflex sensitivity observed in control SHR as compared with control WKY rats (-40%, p less than 0.01) was no longer detectable in the sympathectomized groups. To establish whether the sympathectomy-induced potentiation of the reflex was due to an increase in cardiac responsiveness to vagal stimuli, we subjected separate groups of anesthetized, vagotomized SHR and WKY rats to graded electrical stimulation of the right efferent vagus. The bradycardic effects of vagal stimulation, however, were similar in sympathectomized and control animals.(ABSTRACT TRUNCATED AT 250 WORDS)Keywords
This publication has 16 references indexed in Scilit:
- Evaluation of the baroreceptor-heart rate reflex by 24-hour intra-arterial blood pressure monitoring in humans.Hypertension, 1988
- Inverse relationship between heart rate and blood pressure variabilities in rats.Hypertension, 1987
- The Adrenergic Nervous System in Heart FailureNew England Journal of Medicine, 1984
- Modification of arterial baroreflexes by captopril in essential hypertensionThe American Journal of Cardiology, 1982
- Effects of isometric exercise on the carotid baroreflex in hypertensive subjects.Hypertension, 1982
- Pressor Responsiveness and Cardiovascular Reflex Activity in Spontaneously Hypertensive and Normotensive Rats During Vasopressin InfusionJournal of Cardiovascular Pharmacology, 1981
- Effects of noradrenergic and serotonergic neurons on blood pressure, heart rate and baroreceptor-heart rate reflex of the conscious rabbitJournal of the Autonomic Nervous System, 1981
- Arrhythmias in the first hours of acute myocardial infarctionProgress in Cardiovascular Diseases, 1981
- Autonomic nervous cardiovascular regulation in borderline hypertensionThe American Journal of Cardiology, 1975
- Differentiated Interaction between the Hypothalamic Defence Reaction and Baroreceptor ReflexesActa Physiologica Scandinavica, 1970