JJ McDermott, J Weir, A Faulkner, JT Lightfoot. Autonomic balance is not altered with repeated central hypovolemic exposures . American Physiology Society - Experimental Biology 95 (Atlanta, GA).
We investigated whether neural blood pressure control was altered with repeated exposures to presyncopal limited central hypovolemia (LBNP). Twenty two male subjects were randomly divided into an Experimental group (EXP; n=12) and a Control group (CON; n=10). The EXP received LBNP every day for 10 days and the CON group was exposed to LBNP twice with 10 days separating the exposures. Immediately before the LBNP exposures on Day 1 and 10, resting heart rate data was collected and analyzed using spectral analysis. Additionally, before and after LBNP on a subsample of the subjects (EXP = 6; CON = 5), blood samples were collected for norepinephrine (NE) and epinephrine (EPI) determinations using radioenzymatic techniques. After 10 days, the EXP groupÕs tolerance was increased 12.5% with no change in the CON groupÕs tolerance. The spectral mid-frequency (0.061-0.15 Hz) curveÕs power was unchanged in the EXP group after 10 days of LBNP while the CON groupÕs decreased by 20%. However, we observed no change in the NE or EPI resting or LBNP responses after 10 days of repeated exposures. Therefore, we conclude that repeated central hypovolemia does not alter neural effector mechanisms.
Funded by American Heart Association, Florida Affliate 90GIA/649.