Inverse-orthostasis may induce elevation of blood pressure due to sympathetic activation

Gábor Raffai, László Kocsis, Márta Mészáros, E. Monos, László Dézsi

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Microgravity and simulated microgravity may cause cardiovascular deconditioning, but mechanisms of instantaneous responses to inverse-orthostasis are not studied. Hence, we investigated transient and steady state cardiovascular changes by combining the tilt technique with cardiovascular telemetry. Normotensive and NO-deprived hypertensive Wistar rats were used to analyze responses of mean arterial blood pressure, heart rate, contractility, spontaneous baroreflex sensitivity (sBRS), and autonomic balance. Inverse-orthostasis tests were carried out by 45° head-down tilting (repeated 3 × 5 mins "R", or sustained for 120 mins "S"). In normotensive rats, horizontal control blood pressure was R111.3 ± 1.7/S110.4 ± 2.3 mm Hg and heart rate was R385.2 ± 5.9/S371.1 ± 6.1 BPM. Head-down tilt induced an increase in blood pressure by R5.9/S10.6 mm Hg, while heart rate, contractility, sBRS, and autonomic balance did not change. The hypertensive response was sustained, could be prevented by prazosin (10 mg/kgbw), and augmented by subanesthetic doses of chloralose (26 and 43 mg/kgbw). In NO-suppressed hypertension, control blood pressure and heart rate were R132.4 ± 2.9/S130.0 ± 4.1 mm Hg and R339.2 ± 7.9/S307.2 ± 23.6 BPM, respectively. Head-down tilt further increased blood pressure by R5.1/S10.5 mm Hg. These data demonstrate that conscious rats respond to inverse-orthostasis by sustained elevation of blood pressure independent of NO synthesis. This response is neither due to increased contractility and altered sBRS, nor due to non-specific stress, but probably due to sympathetic activation elicited by gravity-related reflexes, which increase peripheral resistance.

Original languageEnglish
Pages (from-to)287-294
Number of pages8
JournalJournal of Cardiovascular Pharmacology
Volume47
Issue number2
DOIs
Publication statusPublished - Feb 2006

Fingerprint

Dizziness
Baroreflex
Blood Pressure
Heart Rate
Head-Down Tilt
Myocardial Contraction
Weightlessness
Cardiovascular Deconditioning
Arterial Pressure
Telemetry
Chloralose
Prazosin
Gravitation
Vascular Resistance
Reflex
Wistar Rats
Head
Hypertension

ASJC Scopus subject areas

  • Pharmacology
  • Cardiology and Cardiovascular Medicine

Cite this

Inverse-orthostasis may induce elevation of blood pressure due to sympathetic activation. / Raffai, Gábor; Kocsis, László; Mészáros, Márta; Monos, E.; Dézsi, László.

In: Journal of Cardiovascular Pharmacology, Vol. 47, No. 2, 02.2006, p. 287-294.

Research output: Contribution to journalArticle

Raffai, Gábor ; Kocsis, László ; Mészáros, Márta ; Monos, E. ; Dézsi, László. / Inverse-orthostasis may induce elevation of blood pressure due to sympathetic activation. In: Journal of Cardiovascular Pharmacology. 2006 ; Vol. 47, No. 2. pp. 287-294.
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