Adrenergic Drugs (Exam 1) Flashcards
Adrenergic Neurotransmitters
Norepinephrine and Epinephrine
Adrenergic postganlionic neurons primarily release…
norepinephrine
Adrenal medulla primarily releases…
epinephrine
80% E and 20% NE
Tyrosine
Synthesizes norepinephrine and epinephrine
How does tyrosine synthesize NE and E?
Tyrosine –> L-DOPA –> dopamine –> norepinephrine –> epinephrine
Tyrosine hydroxylase (TH)
Rate-limiting enzyme that converts tyrosine into DOPA
Which neurotransmitter has overlapping affinity for same receptors, transporters, and metabolizing enzymes as NE/E?
Dopamine
MAO and COMT enzymes
Breakdown NE and E
Vanillylmandelic Acid (VMA)
Major metabolite for NE and E
MAO
Monoamine Oxidase
COMT
Catechol-O-Methytransferase
Vesicular monoamine transporter (VMAT)
Responsible for uptake in storage vesicles
Norepinephrine Transporter (NET)
Responsible for reuptake into presynaptic terminal
Alpha 2 Receptors
Located presynaptically function as autoreceptors
Antagonist at VG Na+ channels
Decrease signaling
Antagonist at presynaptic VG Ca2+ channels
Decrease signaling
Tyrosine hydroxylase inhibitor
Decreases signaling
COMT inhibitor
Increases signaling
MAO inhibitor
Increases signaling
Antagonist at presynaptic alpha2 receptors
Increase signaling
Alpha1 Receptors (A, B, D)
Gq
Alpha2 Receptors (A, B, C)
Gi
Beta1-3 Receptors
Gs
NE and E are responsible for…
Fight or flight functions
Norepinephrine fight or flight response
Increase HR and BP
Peripheral Vasoconstriction
Epinephrine fight or flight response
Increase HR and BP
Peripheral Vasoconstriction
Increase Lipid Breakdown
Coronary/Bronchial Dilation
Glycogen –> Glucose
Adrenergic signaling in the EYE
Alpha1 - contraction of iris radial muscle causing mydriasis
Beta - increase aqueous humor production
Adrenergic signaling in the HEART
Beta1 - increased heart rate and contractility
Adrenergic signaling in the BLOOD VESSELS
Alpha1 - vasoconstriction
Beta2- vasodilation
Overall effect is vasoconstriction
Adrenergic signaling in the LUNGS
Beta2- relaxation of bronchial smooth muscle leading to bronchodilation
Adrenergic signaling in the GI
Decrease digestion and secretions
Adrenergic signaling in the BLADDER
Beta2.3 - detrusor muscle relaxation
Alpha1 - urinary sphincter and prostate contraction
Overall effect is inhibition of urination
Adrenergic signaling in the APOCRINE SWEAT GLAND
Increased secretion (sweating)
Adrenergic signaling in the MISC. METABOLIC FUNCTIONS
Gluconeogenesis, glycogenolysis
Lipolysis
Renin release
Adrenergic signaling effects
Increase alertness/promotes wakefulness
Reduce pain perception
Focus attention
Beta Blockers
Reduce adrenergic signaling in brain and cause fatigue and decreased alertness
Locus Coeruleus
Produces much of norepinephrine
Important in formation of emotional memories
Alpha1 Affinity for Catecholamine
NE > E
Alpha2 Affinity for Catecholamine
E > NE
Beta1 Affinity for Catecholamine
E = NE
Beta2 Affinity for Catecholamine
E»_space; NE
Alpha1 Binding Effects
Vasoconstriction
Increased blood flow
Increased blood pressure
Mydriasis
Increased closed bladder sphincters
Alpha2 Binding Effects
Inhibits NE, acetylcholine, and insulin release
Beta1 Binding Effects
Increased HR, lipolysis, myocardial contractility, and renin
Beta2 Binding Effects
Vasodilation
Decreased blood flow
Bronchodilation
Increased Gylcogenolysis and glucagon release
Relaxes uterine smooth muscle
Blood Pressure
BP = cardiac output x peripheral vascular resistance
Activation of SNS
Increases blood pressure
Activation of Alpha1 Receptors
Vasoconstriction
Activation of Beta2 Receptors
Vasodilation
Activation of Beta1 Receptors on Heart
Increased heart rate and heart contractility
Activation of Beta1 Receptors on Kidneys
Increase renin release
Beta3 Agonists
Reduce urination
Used in treatment of overactive bladder
Alpha1 Antagonists
Vasodilation - treats hypertension
Prostate muscle relaxation - treats benign prostatic hyperplasia
Beta2 Agonists
Bronchodilation - treats asthma and COPD
Beta Blocker Treatment
Treats heart failure, hypertension, tachycardias, arrythmias, glaucoma
Sympathomimetics
Enhance adrenergic signaling
Direct Acting
Act as agonist at alpha/beta receptors
Indirect Acting
Increase adrenergic signaling without directly activating receptors
Indirect Acting Mechanisms
Inhibition of NET
VMAT inhibition leading to reverse transport of NET
Inhibition of metabolizing enzymes
Catecholamine Structure
Catechol ring and amine-containing side chain
Receptor Affinity
Affinity for adrenergic receptors is reduced when lacking aromatic ring and beta -OH groups
Phenylephrine
Alpha receptor agonist
Low affinity for receptors
Amphetamine
Indirect sympathomimetic
Lacks aromatic and beta OH groups
Does not bind to alpha or beta
Dopamine
Actives adrenergic receptors
Low affinity
Lack of beta OH group
Alpha Receptor Selectivity
Absence of 4-OH group decreases binding to beta receptors
Beta Receptor Selectivity
Larger alkyl chains on amine group increases selectivity
SARs COMT
Adds methyl group to 3-OH
SARs MAO
Oxidizes alpha-carbon leading to removal of amine group
Isoproterenol
Beta receptor selective agonist based on presence of isopropyl group
Drugs Lacking 3-OH Group
Not susceptible to COMT metabolism
Increases oral bioavailability and drug half life
Alpha Carbon Functional Groups
Provide steric hinderance against monoamine oxidase
Increases oral bioavailability and drug half life
Hydrophilicity
Lacking hydroxyl group = more lipophilic
Cross membranes easier and improved oral bioavailability
Antiadrenergic
Decrease adrenergic signaling
Most are direct acting
Metyrosine
Blocks tyrosine hydroxylase
Reduces synthesis of dopamine, norepinephrine, epinephrine
Used in treatment pf pheochromocytoma (adrenal tumor)
Beta Blocker Structure
One aromatic ring and one amine group
Alpha Blocker Structure
One aromatic ring and one amine group