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Action of Dopamine at Different Doses



Dopamine Receptors and Sensitivity

Dopaminergic Receptors: D1 and D2
  • D1

    • Most sensitive Stimulated even at low concentration of dopamine low dose is sufficient to activate them.

    • Present in:

      • Renal blood vessels.

      • Proximal tubular cells.

      • Heart.

Adrenergic receptors
  • β1

    • Moderately sensitive requires relatively high concentration stimulated at moderate doses.

    • Present in heart.

  • α1

    • Least sensitive requires high concentration stimulated only at large doses of dopamine.

    • Present in blood vessels


Actions of Dopamine at Different Doses

Low dose

Stimulates D1 receptors

1. In renal blood vessels vasodilatation maintains/increases renal perfusion increases GFR.

2. In proximal tubular cells decreases sodium reabsorption natriuresis decrease in blood volume decrease preload on heart.

3. In heart Positive ionotropic effect.


Moderated doses

Stimulates β1 receptor in heart

Positive ionotropic.


Large doses

Stimulates α1 receptors in blood vessels

Vasoconstriction

Increased blood pressure

Increased preload on heart.


Dopamine In Heart Failure

  • Actions produced at low to moderate doses are desired. i.e.

    • Maintaining GFR.

    • Natriuretic effect.

    • Positive ionotric effect.

  • Action produced at a large dose is not desired i.e. vasoconstriction.

  • So in heart failure, dopamine should be given in low to moderate doses but not in a large doses.

 

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