Related Experiment Videos
Alpha 1- and alpha 2-adrenoceptor stimulation: changes in venous capacitance in intact dogs
The American Journal of Physiology
|June 1, 1986
Summary
Alpha 1-stimulation with methoxamine hydrochloride increased mean aortic pressure, filling pressure, and blood volume more effectively than alpha 2-stimulation with UK 14304-18 in dogs. This suggests differential effects on peripheral circulation.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
- Adrenoceptor Function
Background:
- Alpha-adrenoceptors play a critical role in regulating peripheral circulation.
- Understanding the distinct effects of alpha-1 and alpha-2 adrenoceptor stimulation is crucial for cardiovascular research.
Purpose of the Study:
- To compare the peripheral circulatory effects of alpha 1-adrenoceptor stimulation (methoxamine hydrochloride) versus alpha 2-stimulation (UK 14304-18).
- To investigate the impact of these stimulations on systemic vascular resistance, arterial pressure, mean circulatory filling pressure, central blood volume, and vascular compliance.
Main Methods:
- 12 intact dogs were used in the study.
- Agents were infused to increase systemic vascular resistance and arterial pressure by 50% and 100%.
- Heart rate was controlled using atropine; hemodynamic parameters were measured, including mean aortic pressure, mean circulatory filling pressure, and central blood volume.
Main Results:
- Methoxamine (alpha-1) significantly increased mean aortic pressure, mean circulatory filling pressure (MCFP), and central blood volume (CBV) without altering cardiac output.
- UK 14304-18 (alpha-2) increased mean aortic pressure but decreased cardiac output, with smaller increases in MCFP and CBV compared to methoxamine.
- Effective vascular compliance decreased with methoxamine but remained unchanged with UK 14304-18, indicating alpha-1 stimulation reduced vascular compliance more significantly.
Conclusions:
- Alpha-1 adrenoceptor stimulation with methoxamine has a more pronounced effect on increasing mean circulatory filling pressure and central blood volume compared to alpha-2 stimulation with UK 14304-18.
- Alpha-1 stimulation leads to a greater reduction in effective vascular compliance than alpha-2 stimulation.
- Both agents effectively decrease unstressed vascular volume, but their impact on overall circulatory dynamics differs significantly.