Both sustained orthostasis and inverse-orthostasis may elicit hypertension in conscious rat

Gábor Raffai, László Dézsi, Márta Mészáros, Márk Kollai, Emil Monos

Research output: Contribution to journalArticle

Abstract

The organism is exposed to diverse orthostatic stimuli, which can induce several acute and chronic adaptive responses. In this study, we investigated hemodynamic responses elicited by short-term and intermediate-term various orthostatic stimuli, using normotensive and hypertensive rat models. Arterial blood pressure and heart rate were measured by telemetry. Hypertension was induced by NO-synthase blockade. Effect of orthostatic and inverse-orthostatic body positions were examined in 45{ring operator} head-up (HUT) or head-down tilt (HDT), either for 5 min duration repeated 3 times each with a 5-min pause "R", or as sustained tilting for 120 min "S". Data are given as mean ± SEM. In normotensives, horizontal control blood pressure was R 115.4 ± 1.4 / S 113.7 ± 1.6 mmHg and heart rate was R 386.4 ± 7.0 / S 377.9 ± 8.8 BPM. HUT changed blood pressure by R < ± 1 (ns) / S 4.6 mmHg (p < 0.05). HDT resulted in augmented blood pressure increase by R 6.2 (p < 0.05) / S 14.4 mmHg (p < 0.05). In NO-deprived hypertension, horizontal control hemodynamic parameters were R 138.4 ± 2.6 / S 140.3 ± 2.7 mmHg and R 342.1 ± 12.0 / S 346.0 ± 8.3 BPM, respectively. HUT and HDT changed blood pressure further by R < ± 1 (ns) / S 5.6 mmHg (p < 0.05) and by R 8.9 (p < 0.05) / S 14.4 mmHg (p < 0.05), respectively. Heart rate changed only slightly or non-specifically. These data demonstrate that both normotensive and hypertensive conscious rats restricted from longitudinal locomotion respond to sustained orthostasis or inverse-orthostasis related gravitational stimuli with moderate or augmented hypertension, respectively.

Original languageEnglish
Pages (from-to)415-419
Number of pages5
JournalActa Astronautica
Volume60
Issue number4-7 SPEC. ISS.
DOIs
Publication statusPublished - Feb 1 2007

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ASJC Scopus subject areas

  • Aerospace Engineering

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