Effects of propranolol on the impulse activity of cardiovascular sympathetic afferent fibers

Federico Lombardi, Carlo Casalone, Gabriella Malfatto, Tomaso Gnecchi Ruscone, Rodolfo Casati, Alberto Malliani

Research output: Contribution to journalArticle

Abstract

The influence of β-adrenergic receptor blockade on the impulse activity of 21 cardiovascular sympathetic afferent nerve fibers (11 from the thoracic aorta, 10 from the pulmonary veins), isolated from the left sympathetic rami communicantes T-3 and T-4 was studied in anesthetized, vagotomized cats. Aortic pressure, heart rate, and neural discharge were recorded during control conditions and during brief aortic occlusions of comparable amplitude and duration. Administration of (dl-propranolol (0.2-0-4 mg/kg) did not modify aortic pressure or neural discharge of the fibers during control conditions, although, as expected, heart rate was diminished. (dl -Propranolol administration did change the response of cardiovascular sympathetic afferents to similar aortic pressure increases. Before drug administration, aortic occlusion caused a significant increase in neural discharge of both aortic and pulmonary vein sympathetic afferent fibers, from 0.52 ± 0.12 to 1.64 ± 0.31 and from 0.67 ± 0.10 to 2.08 ± 0.25 impulses/sec, respectively (p <0.05). After (dl -propranolol administration, comparable increases in aortic pressure resulted in slight but not significant increases in neural discharge of aortic and pulmonary vein fibers. Administration of d-propranolol (0.4-0.6 mg/kg), which possesses only membrane-stabilizing properties, did not modify the firing rate of four pulmonary sympathetic afferents, which subsequently decreased their response to pressure rises after administration of (dl -propranolol. These results indicate that β-adrenergic receptor blockade reduces the responsiveness to hemodynamic stimuli of sympathetic cardiovascular afferent fibers that are capable of mediating excitatory pressor reflexes.

Original languageEnglish
Pages (from-to)50-55
Number of pages6
JournalHypertension
Volume8
Issue number1
Publication statusPublished - 1986

Keywords

  • Arterial hypertension
  • Cardiovascular sympathetic afferent fibers
  • Positive feedback reflexes
  • β-blockers

ASJC Scopus subject areas

  • Internal Medicine

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