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Systemic angiotensin-induced drinking in the dog: a physiological phenomenon
The Journal of Physiology
|March 1, 1978
Summary
Angiotensin II is the most potent stimulator of thirst in dogs, triggering drinking within physiological limits. Satiety mechanisms, not fatigue, explain reduced drinking during prolonged infusions.
Area of Science:
- Physiology
- Neuroscience
- Endocrinology
Background:
- The renin-angiotensin system (RAS) plays a crucial role in regulating blood pressure and fluid balance.
- Understanding the dipsogenic effects of RAS components is vital for comprehending thirst regulation.
Purpose of the Study:
- To investigate the dipsogenic effects of individual components of the renin-angiotensin system in dogs.
- To determine the relative potencies and effective doses of various RAS peptides in stimulating drinking behavior.
- To elucidate the mechanisms underlying thirst satiation during prolonged RAS activation.
Main Methods:
- Intravenous and intracarotid infusions of angiotensin II, angiotensin I, synthetic renin substrate, angiotensin III, and renin were administered to dogs in water balance.
- Dose-response relationships and infusion rates were systematically varied.
- Water intake was measured, and the effects of delayed water access and fluid preloads were assessed.
Main Results:
- Angiotensin II was the most potent and rapidly acting dipsogen, with effective infusion rates within physiological and mildly pressor ranges.
- Angiotensin I, synthetic renin substrate, and angiotensin III showed weaker dipsogenic effects compared to angiotensin II.
- Renin induced drinking, but with a slower onset and longer duration.
- Water intake was more dependent on the rate than the duration of angiotensin II infusion.
- Satiety mechanisms, not tachyphylaxis, were responsible for reduced drinking during prolonged angiotensin II infusions.
- Intracarotid infusions generally mimicked intravenous effects, though renin was less effective via this route.
Conclusions:
- Circulating angiotensin II is a significant dipsogenic factor, likely involved in the thirst associated with hypovolemia and dehydration.
- The study highlights the differential potencies of RAS components in eliciting drinking.
- Thirst satiation during sustained angiotensin II infusion is mediated by physiological satiety signals.