Author:
Raffai G,Csekő C,Nádasy G,Monos E
Abstract
Sustained orthostasis elicits the elevation of arterial blood
pressure (BP) via sympathetic activation in conscious Wistar rats
for at least 2 hours. We tested the hypothesis whether vestibular
apparatus plays a role in BP and heart rate (HR) control in
response to prolonged gravitational stress. BP and HR responses
to 45º head-up for either 2 or 24 hours were monitored by
telemetry. Vestibular lesions (VL) were performed by a modified
microsurgical-chemical technique. Horizontal BP and HR were not
influenced by VL preceding 2-hour tilt. VL abolished the sustained
2-hour BP response to head-up tilt (8.3±0.9 mm Hg relative to
horizontal values) while suppressed HR transiently only. VL
eliminated diurnal BP fluctuations and decreased HR in horizontal
position for 24 hours. Head-up tilt for 24 hours increased BP and
HR progressively in intact animals, raising their daily average
value by 5.6±0.7 mm Hg and 22.2±6 BPM, respectively. VL
resulted in an initial BP rise followed by progressive BP reduction
in response to long-term head-up tilt (4±2.2 mm Hg) without
eliminating the tachycardia (34.4±5.4 BPM). Thus, blockade of
labyrinthine inputs attenuates the BP responses elicited by both
intermediate and long-term gravitational stress of orthostatic
type. However, other sensory inputs derived from non-vestibular
cues (e.g. proprioceptive, visual, visceral, cutaneous etc.) seem
to be effective enough to maintain BP normal.
Publisher
Institute of Physiology of the Czech Academy of Sciences
Subject
General Medicine,Physiology
Cited by
3 articles.
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