- Norepinephrine (Noradrenaline) is a neurotransmitter and hormone that plays a key role in the body’s “fight-or-flight” response.
- It is produced primarily in the adrenal medulla and by certain neurons in the central and peripheral nervous systems.
Chemical Structure & Formula
- Chemical Formula: C₈H₁₁NO₃
- Structure:
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Mechanism of Action (Detailed)
- It is primarily acts on α1, α2, and β1 adrenergic receptors but has little effect on β2 receptors.
- α1 Activation: Leads to vasoconstriction, increasing blood pressure.
- α2 Activation: Provides feedback inhibition, reducing further norepinephrine release.
- β1 Activation: Increases heart rate and myocardial contractility.
Physiological Effects
- Cardiovascular: Increases blood pressure via vasoconstriction (α1), increases heart rate and cardiac output (β1).
- Metabolic: Slight hyperglycemia due to glycogenolysis activation.
- Renal: Reduces renal perfusion due to vasoconstriction.
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Side Effects of Norepinephrine
- Hypertension (due to excessive vasoconstriction)
- Reflex bradycardia (via baroreceptor reflex)
- Arrhythmias
- Tissue necrosis (if extravasation occurs)
Clinical Uses of Norepinephrine
- Septic shock – To maintain blood pressure.
- Acute hypotension – In cases of severe hypotension.
- Cardiogenic shock – As an emergency drug.
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