Key Points
- This research aims to analyze the effects of methoxamine and nitroglycerin on coronary dimensions and resistance in conscious dogs.
- Eight conscious dogs were studied using an ultrasonic dimension gauge to measure left circumflex coronary dimensions.
- Methoxamine (50 mug/kg per min) and nitroglycerin (25 mug/kg) were administered to assess their effects on coronary resistance and arterial pressure.
- Total coronary resistance was determined from measurements of arterial pressure and coronary blood flow.
- Methoxamine caused a sustained reduction in left circumflex diameter by 9+/-2%, while coronary resistances rose by 108+/-29% and 92+/-14%.
- Nitroglycerin induced an initial decrease in coronary dimensions, followed by an increase, with large vessel resistance falling by 18+/-2%.
- Total coronary resistance showed a slight rise of 11+/-4% after nitroglycerin administration.
Structured PICO
PPopulation8 conscious dogs
IInterventionMethoxamine (50 mug/kg per min) and Nitroglycerin (25 mug/kg)
CComparatorBaseline/control levels
OOutcomeLarge vessel (left circumflex) coronary dimensions and total coronary resistancesurrogate
Alpha-adrenergic stimulation with methoxamine actively constricts large coronary arteries despite increased distending pressure, while nitroglycerin dilates them, demonstrating active vasoregulation in conscious dogs.