Abstract
Cardiovascular functions were studied in semi-arboreal rat snakes (Elaphe obsoleta) following long-term, intermittent exposure to +1.5G z (head-totail acceleration) on a centrifuge. Snakes were held in a nearly straight position within horizontal plastic tubes during periods of centrifugation. Centrifugal acceleration, therefore, subjected snakes to a linear force gradient with the maximal force being experienced at the tail. Compared to non-centrifuged controls,G z-acceimated snakes showed greater increases of heart rate during head-up tilt or acceleration, greater sensitivity of arterial pressure to circulating catecholamines, higher blood levels of corticosterone, and higher blood ratios of prostaglandin F2α/prostaglandin E2. Cardiovascular tolerance to increased gravity during gradedG z acceleration was measured as the maximum (caudal) acceleration force at which carotid arterial blood flow became null. When such tolerances were adjusted for effects of body size and other continuous variables incorporated into an analysis of covariance, the difference between the adjusted mean values of control and acelimated snakes (2.37 and 2.84G z, respectively) corresponded closely to the 0.5G difference between the acelimationG (1.5) and Earth gravity (1.0). As in other vertebrates, cardiovascular tolerance toG z stress tended to be increased by acclimation, short body length, high arterial pressure, and comparatively large blood volume. Voluntary body movements were important for promoting carotid blood flow at the higher levels ofG z stress.
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Abbreviations
- bpm :
-
heat beats per minute
- FV :
-
fluid volume
- G :
-
gravitational or acceleration force
- G z :
-
gravitational or acceleration force in the head-to-tail direction
- Hct :
-
hematocrit
- HIP :
-
hydrostatic indifferent point
- PGE :
-
prostaglandin E2
- PGF :
-
prostaglandin F2a
- PGFM :
-
stable metabolite of PGF
- RCV :
-
red cell volume
- RIA :
-
radioimmunoassay
- SAS :
-
statistical analysis system
- TBV :
-
total blood volume
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Communicated by L.C.-H. Wang
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Lillywhite, H.B., Ballard, R.E. & Hargens, A.R. Cardiovascular responses of semi-arboreal snakes to chronic, intermittent hypergravity. J Comp Physiol B 166, 241–253 (1996). https://doi.org/10.1007/BF00262868
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DOI: https://doi.org/10.1007/BF00262868