Excited α1

Arouses blood vessel wall α2

Positivity

Increased cardiac excitatory metabolites (adenosine, etc.)

small dose

large dose

Constrict blood vessels in the esophageal and gastric mucosa, producing local hemostasis

Use alpha blocker phentolamine for local infiltration injection to dilate blood vessels

Excites the heart, increases myocardial metabolism, and increases myocardial oxygen consumption

But overdose can also cause arrhythmia

The effect depends on the distribution and number of α and β receptors on the vascular smooth muscle of each organ and the dosage.

biphasic reaction

The pressor effect of epinephrine can be reversed by pre-administration of alpha-blocking drugs

Activates bronchial smooth muscle β2 receptors

Stimulate alpha receptors in bronchial mucosa and blood vessels and contract

Promote aqueous outflow

Vasodilation at low concentrations

High concentrations of dopamine stimulate cardiac β1 receptors, enhance myocardial contractility, and increase cardiac output.

Large doses excite alpha receptors, constrict blood vessels, and increase blood pressure.

Acts on D1 receptors at low concentrations

In large doses, it excites α-receptors in renal blood vessels and causes significant contraction of renal blood vessels.

Two factors: gradual saturation of receptors and gradual depletion of transmitters

Can be used to prevent hypotension during spinal anesthesia

positive inotropy

positive frequency

Dilate blood vessels, mainly skeletal muscle blood vessels

dilate bronchial smooth muscle

Inhibit the release of bronchial allergic substances

But there is no contraction effect of bronchial mucosal blood vessels

It has a pacing effect on the stopped heart and restores the beating of the heart.