Improved thermoregulatory and autonomic responses contribute to reduced fatigue and faster recovery from exertional heat stress by sympatholytic treatment with clonidine
Abstract
We investigated the effect of clonidine (C, 33 μg/kg/day, osmotic pumps) on thermoregulatory and autonomic responses to chronic exposure to exertional (ExHS) and non‐exertional (HS) heat stress in rats. Blood pressure (BP), heart rate (HR) and core temperature (Tc) were recorded telemetrically before, during, and after a 5‐day (twice a day) ExHS, HS, or sham protocol. During the five protocol days, nocturnal Tc and HR were elevated in placebo‐treated rats (P) exposed to ExHS and HS. C reduced these increases in Tc and HR, suggesting improved thermoregulation. Nocturnal BP in P was more elevated in ExHS than in HS. C reduced nocturnal BP in ExHS, suggesting increased sympathetic tone in P exposed to ExHS. Similarly, in P, low frequency systolic BP variability (LFSYS), reflecting sympathetic modulation of vascular tone, was more elevated in ExHS than in HS and C reduced this elevated LFSYS in ExHS. Likely due to fatigue, exploratory behavior (open field test) declined during the 5 protocol days in ExHS and HS. In ExHS, this effect was blunted by C. Furthermore, recovery of exploratory behavior in ExHS was more pronounced and faster in C‐treated rats compared to P. C improves thermoregulation and reduces sympathetic responses to chronic exposure to ExHS. These effects of C may reduce fatigue and contribute to faster recovery following chronic exposure to ExHS.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2013
- Source ID
- 10.1096/fasebj.27.1_supplement.1133.4
Entities
People
- Ann M Moss
- Harald Martin Stauss
- Kevin C. Kregel
- Navita Choudhary
Organizations
- United States Department of Defense
- University of Iowa