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Sympathomimetic drugs (also known as adrenergic drugs and adrenergic amines) are stimulant compounds which mimic the effects of endogenous agonists of the sympathetic nervous system. Examples of sympathomimetic effects include increases in heart rate , force of cardiac contraction , and blood pressure . [ 1 ]
The second hypothesis found support from 1906 to 1913, when Henry Hallett Dale explored the effects of adrenaline (which he called adrenine at the time), injected into animals, on blood pressure. Usually, adrenaline would increase the blood pressure of these animals. Although, if the animal had been exposed to ergotoxine, the blood pressure ...
The alpha-2 (α 2) adrenergic receptor (or adrenoceptor) is a G protein-coupled receptor (GPCR) associated with the G i heterotrimeric G-protein. It consists of three highly homologous subtypes, including α 2A-, α 2B-, and α 2C-adrenergic. Some species other than humans express a fourth α 2D-adrenergic receptor as well. [1]
Additional hypotensive effects may occur when patients are taking beta-1 blockers with other antihypertensive drugs such as nitrates, PDE inhibitors, ACE inhibitors and calcium channel blockers. [17] The combination of beta blockers and antihypertensive drugs will work on different mechanism to lower blood pressure. [17]
Alpha-adrenergic agonists are a class of sympathomimetic agents that selectively stimulates alpha adrenergic receptors. The alpha-adrenergic receptor has two subclasses α 1 and α 2. Alpha 2 receptors are associated with sympatholytic properties. Alpha-adrenergic agonists have the opposite function of alpha blockers.
However, some side effects can occur, such as palpitation, tremor, elevated blood pressure, and anxiety. [23] Yohimbe bark contains both α 1 and α 2 adrenergic receptors blocking alkaloids . Phentolamine , a non-selective alpha blocker, has also been tested to treat erectile dysfunction.
Together, the effects increase peripheral blood pressure, but decrease central blood pressure. This can have larger effects on those with diabetes. Hypoglycemia may cause greater arterial wall stiffness and less elasticity, which in turn decreases blood pressure and increases the heart's workload. [17]
In 1900, Reid Hunt, a pharmacologist (1870-1948), realised a fall in blood pressure in rabbits after removing adrenaline (epinephrine) from adrenal glands extract. While he initially attributed this effect to choline , he later discovered acetylcholine was 100 000 times more potent in lowering blood pressure.