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Central osmoregulatory influences on thermoregulation
M J McKinley1, R M McAllen, D Whyte
1Howard Florey Institute, University of Melbourne, Melbourne, Victoria Australia. michael.mckinley@florey.edu.au
Clinical and Experimental Pharmacology & Physiology
|December 11, 2007
Summary
Dehydrated mammals reduce evaporative cooling, raising core body temperature. Drinking water quickly restores cooling via a reflex overriding osmoreceptor inhibition, preventing overheating.
Area of Science:
- Physiology
- Thermoregulation
- Mammalian Physiology
Background:
- Mammals use evaporative cooling (sweating, panting) to maintain core body temperature under heat load.
- Evaporative cooling leads to fluid loss, potentially causing dehydration, hypertonicity, and hypovolemia.
- Dehydration inhibits evaporative cooling, leading to elevated core body temperatures in mammals.
Purpose of the Study:
- To investigate the mechanisms inhibiting evaporative cooling in dehydrated mammals.
- To identify the role of osmoreceptors in suppressing panting and sweating.
- To understand the rapid resumption of cooling responses upon water ingestion.
Main Methods:
- Review of existing evidence on evaporative cooling and dehydration in mammals.
- Analysis of the effects of plasma osmotic pressure on thermoregulatory responses.
- Focus on osmoreceptor location and function, particularly in sheep.
Main Results:
- Increased plasma osmotic pressure inhibits panting and sweating in mammals.
- Cerebral osmoreceptors, likely in the lamina terminalis, mediate panting suppression in dehydrated sheep.
- Drinking water rapidly reactivates panting and sweating before gut absorption, overriding osmoreceptor inhibition.
Conclusions:
- Osmoreceptors in the lamina terminalis play a key role in suppressing evaporative cooling during dehydration.
- A drinking-induced reflex can override osmoreceptor signals, rapidly restoring thermoregulation.
- This rapid reflex is crucial for preventing dangerous core temperature increases in dehydrated mammals.
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