- Title
- Venous hydrostatic indifference point as a marker of postnatal adaptation to orthostasis in swine
- Creator
- Buckner, Phillip S.; Quail, Anthony W.; Cottee, David B. F.; White, Saxon William
- Relation
- Journal of Applied Physiology Vol. 87, Issue 3, p. 882-888
- Relation
- http://jap.physiology.org/cgi/content/abstract/87/3/882
- Publisher
- American Physiological Society
- Resource Type
- journal article
- Date
- 1999
- Description
- The postulate that venous adaptation assists postural baroreflex regulation by shifting the hydrostatic indifference point (HIP) toward the heart was investigated in eight midazolam-sedated newborn piglets. Whole body head-up (+15, +30, and +45°) and head-down (-15 and -30°) tilt provided a physiological range of orthostatic strain. HIP for all positive tilts shifted toward the heart (P < 0.05), +45° HIP shifted most [6.7 ± 0.3, 5.9 ± 0.5, and 3.6 ± 0.3 (SE) cm caudal to right atrium on days 1, 3, and 6, respectively]. HIP for negative tilts (3.0 ± 0.2 cm caudal to right atrium) did not shift with postnatal age. Euthanasia on day 6 caused 2.1 ± 0.3-cm caudal displacement of HIP for positive and negative tilts (P < 0.05). HIP proximity to right atrium was not altered by α-, β-adrenoceptor and cholinoceptor blockade on day 5. It is concluded that early HIP migration reflects enhancement of venous pressure control to head-up orthostatic strain. The effect is independent of baroreflex-mediated adrenoceptor and cholinoceptor mechanisms.
- Subject
- postural baroreflex; tilt; newborn; swine; autonomic blockade
- Identifier
- uon:2825
- Identifier
- http://hdl.handle.net/1959.13/31813
- Identifier
- ISSN:8750-7587
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