Adrenergic Receptors

Adrenergic Receptors

• Also known as adrenoceptors
• Respond to the neurotransmitter norepinephrine (NE) and epinephrine (E)
• Two main categories: alpha (α) and beta (β) receptors

Alpha Receptors

• Further divided into two subtypes: α1 and α2
• α1 receptors:
  • Found in smooth muscle and exocrine glands
  • Activation causes vasoconstriction, increased blood pressure, and pupil dilation
• α2 receptors:
  • Found in pancreatic islet cells, adipose tissue, and some neurons
  • Activation causes decreased insulin secretion, increased glucagon secretion, and decreased lipolysis

Beta Receptors

• Further divided into three subtypes: β1, β2, and β3
• β1 receptors:
  • Found in heart and kidney
  • Activation causes increased heart rate, contractility, and renin secretion
• β2 receptors:
  • Found in smooth muscle, skeletal muscle, and liver
  • Activation causes relaxation of smooth muscle, increased muscle contraction, and increased glycogenolysis
• β3 receptors:
  • Found in adipose tissue
  • Activation causes increased lipolysis

Adrenergic Agonists

• Direct-acting agonists:
  • Stimulate adrenergic receptors directly
  • Examples: norepinephrine, epinephrine, isoproterenol, and phenylephrine
• Indirect-acting agonists:
  • Increase the release or inhibit the reuptake of norepinephrine
  • Examples: amphetamine and cocaine

Adrenergic Antagonists

• Alpha blockers:
  • Block α receptors
  • Examples: phentolamine and prazosin
• Beta blockers:
  • Block β receptors
  • Examples: propranolol and atenolol

Clinical Applications

• Adrenergic agonists:
  • Used to treat anaphylaxis, asthma, and hypotension
  • Used as decongestants and in ophthalmology
• Adrenergic antagonists:
  • Used to treat hypertension, anxiety, and glaucoma
  • Used in cardiology to reduce heart rate and blood pressure

Adrenergic Receptors

• Respond to neurotransmitters norepinephrine (NE) and epinephrine (E)
• Classified into two main categories: alpha (α) and beta (β) receptors

Alpha Receptors

• Divided into two subtypes: α1 and α2
• α1 receptors:
  • Found in smooth muscle and exocrine glands
  • Activation causes vasoconstriction, increased blood pressure, and pupil dilation
• α2 receptors:
  • Found in pancreatic islet cells, adipose tissue, and some neurons
  • Activation causes decreased insulin secretion, increased glucagon secretion, and decreased lipolysis

Beta Receptors

• Divided into three subtypes: β1, β2, and β3
• β1 receptors:
  • Found in heart and kidney
  • Activation causes increased heart rate, contractility, and renin secretion
• β2 receptors:
  • Found in smooth muscle, skeletal muscle, and liver
  • Activation causes relaxation of smooth muscle, increased muscle contraction, and increased glycogenolysis
• β3 receptors:
  • Found in adipose tissue
  • Activation causes increased lipolysis

Adrenergic Agonists

• Direct-acting agonists:
  • Stimulate adrenergic receptors directly
  • Examples: norepinephrine, epinephrine, isoproterenol, and phenylephrine
• Indirect-acting agonists:
  • Increase the release or inhibit the reuptake of norepinephrine
  • Examples: amphetamine and cocaine

Adrenergic Antagonists

• Alpha blockers:
  • Block α receptors
  • Examples: phentolamine and prazosin
• Beta blockers:
  • Block β receptors
  • Examples: propranolol and atenolol

Clinical Applications

• Adrenergic agonists:
  • Used to treat anaphylaxis, asthma, and hypotension
  • Used as decongestants and in ophthalmology
• Adrenergic antagonists:
  • Used to treat hypertension, anxiety, and glaucoma
  • Used in cardiology to reduce heart rate and blood pressure

Learn about adrenergic receptors, also known as adrenoceptors, which respond to neurotransmitters norepinephrine and epinephrine, and their subdivisions into alpha and beta receptors. Understand their functions and locations in the body.