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Cardiovascular, thermoregulatory, and autonomic effects of pretreatment with clonidine (C) or lisinopril (L) on recovery from exertional heat stress (ExHs) in rats
Author(s) -
Stauss Harald Martin,
Liaboe Frederick O.,
Ingram Robert,
Leon Lisa R.,
Kregel Kevin C.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1052.4
Subject(s) - heart rate , blood pressure , medicine , heart rate variability , endocrinology , thermoregulation , cardiac function curve , placebo , clonidine , autonomic nervous system , anesthesia , heart failure , alternative medicine , pathology
During recovery from ExHs, high frequency (HF) heart rate (HR) variability is reduced and low frequency (LF) blood pressure (BP) variability is elevated. Thus, altered autonomic function may contribute to ExHs‐induced morbidity and mortality. We studied recovery from ExHs following pretreatment with C (30mg/kg/day, n=11), L (3mg/kg/day, n=8), or placebo (P, n=8) in rats. Drugs were given 24 h and immediately before ExHs (running wheel, 6–9 m/min, 39°C). BP, HR, and core temperature (Tc) were recorded telemetrically. During recovery from ExHs, BP was lower in L (109±3 mmHg) compared to C (117±3 mmHg) or P (118±3 mmHg). HR and Tc were lower in C (330±8 bpm; 37.8±0.1 o C) compared to L (373±10 bpm; 38.2±0.2 o C) and P (360±7 bpm; 38.1±0.1). LF HR variability (sympathetic cardiac modulation) was reduced in L (9.3±0.9 %) compared to C (16.0±2.3 %) and P (15.1±2.0 %), while LF BP variability (sympathetic vascular modulation) was reduced in L (3.4±0.6 mmHg 2 ) and C (3.9±0.5 mmHg 2 ) compared to P (5.5±0.9 mmHg 2 ). In conclusion, C improves thermoregulation following ExHs as indicated by a lower Tc. Because of the linear relationship between HR and metabolic rate, the lower HR in C suggests that this effect may be mediated by a lower metabolic rate. Both drugs reduce sympathetic modulation of cardiovascular end‐organ function, which may contribute to improved recovery following ExHs. Support: USAMRMC; not official US Army or DoD policy.