I. Effects: Alpha Receptor General

  1. Vascular smooth muscle
    1. Skin and skeletal muscle vessel constriction
    2. Splanchnic vessel constriction
  2. Gastrointestinal
    1. Myenteric Plexus Inhibition
  3. Genitourinary
    1. Pregnant Uterus contraction
    2. Penis and seminal Vesicle ejaculation
  4. Skin
    1. Pilomotor smooth muscle contraction
    2. Apocrine gland contraction
  5. Metabolic
    1. Gluconeogenesis
    2. Glycogenolysis

II. Effects: Alpha 1 Receptors

  1. Vascular smooth muscle postsynaptic neurons
    1. Vasoconstriction
  2. Myocardium
    1. Positive Inotrope
    2. Negative Chronotrope
  3. Eye
    1. Radial muscle contraction
  4. Gastrointestinal and Genitourinary
    1. Sphincter (e.g. anus) contraction

III. Effects: Alpha 2 Receptors

  1. Peripheral Alpha 2 Receptors
    1. Vascular Smooth Muscle (mixed effect)
      1. Modulates large vessel tone
      2. Arteriolar and venous Vasoconstriction
      3. Opposes alpha 1 receptor Vasoconstriction
        1. Inhibits Norepinephrine release
        2. Decreases adrenergic activity
    2. Gastrointestinal
      1. Smooth muscle wall relaxation
    3. Metabolic
      1. Fat Cell Lipolysis
  2. Central Alpha 2 Receptors (CNS)
    1. Inhibits Locus Ceruleus reflex arc
    2. Peripheral vasodilatation

IV. Medications: Alpha Adrenergics

  1. Alpha Adrenergic Agonist (Alpha Adrenergic Receptor)
    1. Alpha Non-Specific
      1. Epinephrine
      2. Norepinephrine
    2. Alpha 1 Selective
      1. Phenylephrine
      2. Methoxamine
    3. Alpha 2 Selective
      1. Clonidine (See Central Adrenergic Agonist)
      2. Alpha-methylnorepinephrine
  2. Alpha Receptor Antagonist
    1. Alpha Non-Specific
      1. Phentolamine
    2. Alpha 1 Selective
      1. Prazosin (See Alpha Adrenergic Antagonist)
      2. Phenoxybenzamine
    3. Alpha 2 Selective
      1. Yohimbine
      2. Tolazoline

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