Key Points
- To determine how angiotensin-induced blood pressure elevation alters heart rate and total body oxygen consumption compared to phenylephrine in squirrel monkeys exposed to cold temperatures.
- Monitored systemic arterial blood pressure, heart rate, and total body oxygen consumption in unanesthetized squirrel monkeys during ambient exposure to 10 °C versus baseline values at 28 °C.
- Administered continuous intravenous infusions of phenylephrine (5–50 µg/kg·min) and angiotensin (0.05–1.0 µg/kg·min) to induce experimental elevations in arterial blood pressure under cold conditions.
- Exposure to 10 °C increased baseline oxygen consumption, heart rate, and systemic arterial blood pressure above levels recorded at 28 °C.
- Phenylephrine infusion increased blood pressure while triggering proportional reflex decreases in both heart rate and oxygen uptake via sinoaortic baroreceptors.
- Angiotensin produced equivalent blood pressure elevations to phenylephrine but caused significantly smaller reflex reductions in both heart rate and oxygen uptake.
Structured PICO
Does angiotensin modulate baro-reflexive responses to elevation in blood pressure compared to phenylephrine in squirrel monkeys?
PPopulationUnanesthetized squirrel monkeys exposed to an ambient temperature of 10 degrees C
IInterventionIntravenous infusion of angiotensin (0.05-1.0 microgram/kg-min)
CComparatorIntravenous infusion of phenylephrine (5-50 microgram/kg-min)
OOutcomeChanges in heart rate (HR) and total body oxygen consumption (VO2) in response to blood pressure elevationsurrogate
Angiotensin appears to modulate baro-reflexive reductions in heart rate and oxygen consumption in response to blood pressure elevation, likely via central nervous system action.