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Splanchnic sympathetic nerve activity and circulating catecholamines in the hyperthermic rat.
C V Gisolfi1, R D Matthes, K C Kregel
1Department of Exercise Science, University of Iowa, Iowa City 52242.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 1, 1991
Summary
Environmental heating increases plasma catecholamines and splanchnic sympathetic nerve activity (SNA) in rats. This response is linked to hyperthermia, elevated heart rate, and significant changes in blood chemistry.
Area of Science:
- Physiology
- Environmental Stress Response
- Cardiovascular Regulation
Background:
- Mechanisms of splanchnic vascular resistance changes during heating are unclear.
- The role of catecholamines and sympathetic nervous system (SNA) in hyperthermia is not fully understood.
Purpose of the Study:
- To investigate the effects of environmental heating on plasma catecholamine levels.
- To assess splanchnic sympathetic nerve activity (SNA) during heat stress.
- To examine associated changes in blood chemistry during hyperthermia.
Main Methods:
- Rats were exposed to controlled environmental heating, with core temperatures (Tc) monitored.
- Plasma catecholamine (norepinephrine, epinephrine) and electrolyte concentrations were measured.
- Splanchnic sympathetic nerve activity (SNA) was directly quantified in anesthetized rats.
Main Results:
- Plasma norepinephrine and epinephrine significantly increased as core temperature rose from 41°C to 43°C.
- Hyperkalemia and lactacidemia were observed at elevated core temperatures.
- Splanchnic SNA significantly increased as core temperature exceeded 39°C.
Conclusions:
- Environmental heating activates the sympathetic nervous system, indicated by increased SNA and catecholamines.
- These physiological responses are associated with significant metabolic and electrolyte disturbances during hyperthermia.
- Findings provide insight into the body's response to severe heat stress.