Adrenergic Stimulants Flashcards
Where does norepinephrine (NE) synthesis occur?
In the presynaptic cell
What enzyme converts the precursor dopamine into norepinephrine (NE)?
Dopamine-β-hydroxylase
How is epinephrine (Epi) synthesized from norepinephrine?
NE is metabolized by phenylethanolamine N-methyltransferase to produce epinephrine
Why are NE and E stored in synaptic vesicles in the presynaptic cell ?
To protect them from degradation and keep them in a ready-to-release format
What triggers the release of norepinephrine and epinephrine from the presynaptic cell?
An action potential
How does NE or Epi get released into the synaptic cleft?
By synaptic vesicle fusion with the synaptic membrane
What happens after NE or Epi is released into the synaptic cleft?
They bind to adrenergic receptors on the surface postsynaptic cell
How is norepinephrine or epinephrine removed (disposition) from the synaptic cleft?
Through reuptake into the presynaptic cell
What transporter is responsible for norepinephrine reuptake and is the purpose?
Norepinephrine Reuptake Transporter (NET)
To recycle the neurotransmitter and terminate the signal
What are the subtypes of adrenergic receptors?
α1, α2, β1, β2, and β3.
What is the primary effect of α adrenergic receptors?
Mostly excitatory, with the exception of α2.
Where is α1 receptor located and what is its effect?
Located in smooth muscle and generally causes excitation (e.g., vasoconstriction).
Where is α2 receptor located and what is its effect?
Located in nerve terminals (presynaptic) and inhibits NE release.
Where is β1 receptor located and what is its effect?
Located in the heart and has an excitatory effect (increases heart rate and contractility).
Where is β2 receptor located and what is its effect?
Located in the lungs, GI tract, uterus, vascular smooth muscle, liver, and skeletal muscle, typically causing inhibitory effects (e.g., bronchodilation, relaxation of smooth muscle).
Where is β3 receptor located and what is its effect?
Located in fat cells, where it regulates lipolysis.
How does activation of adrenergic receptors affect target organs?
It can either activate or inactivate the target organ depending on the receptor type on the organ.
What are drugs that activate the sympathetic nervous system called?
Sympathomimetic drugs.
What is epinephrine used for in dentistry?
It causes vasoconstriction, slowing the diffusion of anesthetic, allowing less anesthetic to be used.
What is the main effect of epinephrine in the body?
Endogenous ligand that activates adrenergic receptors, including vasoconstriction in local anesthesia and bronchodilation in asthma treatment.
What is pseudoephedrine (Sudafed) used for?
It relieves nasal congestion by constricting nasal blood vessels and decreasing mucus production.
What receptors does pseudoephedrine primarily act on?
It is an α1 receptor agonist, causing vasoconstriction in the nasal cavity and potentially raising blood pressure.
What is clonidine (Catapres) used for?
It is used to decrease blood pressure by activating α2 receptors in the brainstem, reducing NE and EPI release.
What secondary effect does clonidine have?
It reduces NE release at presynaptic α2 autoreceptors, contributing to vasodilation.
What is dobutamine (Dobutrex) used for?
It is used to treat congestive heart failure by stimulating β1 receptors to increase cardiac contractile force.
What is albuterol used for?
It is a selective β2 receptor agonist used to treat bronchial asthma by increasing bronchial dilation.
Drugs that act on the Sympathetic Nervous System:
epinephrine
pseudoephedrine
clonidine
dobutamine
albuterol:
How does amphetamine act as an adrenergic agonist?
It stimulates the release of biogenic amines, including NE and dopamine, from nerve endings.
How does cocaine act as an adrenergic agonist?
It selectively blocks the Norepinephrine Reuptake Transporter (NET), increasing NE levels in the synapse.
Drugs that indirectly act Adrenergic Agonists:
amphetamine
cocaine
