Unit 4: Adrenergic Agonists Flashcards
Stimulation of the adrenal glands causes secretion of…
epinephrine and norepinephrine
The drugs that cause effects similar to epinephrine or norepinephrine are called _____ or ____
adrenomimetics
sympathomimetics
The adrenoreceptors are …
alpha
beta
dopamine
define SELECTIVITY
drug binds preferentially to one subset of adrenoreceptors
define SPECIFICITY
near absolute selectivity; also, some drugs interact with more classes of receptors at higher doses/concentration
list 3 terms that describe the desensitization that happens when a cell or tissue is exposed to an agonist over time, and that cell/tissue becomes less responsive to further stimulation from the agent
tolerance
refractoriness
tachyphylaxis
major action that occurs with stimulation of alpha 1 receptors
smooth muscle contraction
alpha 1 receptors are located…
eye hair shaft prostate heart vascular smooth muscle
stimulation of ALPHA 1 RECEPTORS causes _____ in the EYE
contraction of muscle –> dilates pupil
stimulation of ALPHA 1 RECEPTORS causes ____ in the HAIR
erection
stimulation of ALPHA 1 RECEPTORS causes ____ in the PROSTATE
contraction
stimulation of ALPHA 1 RECEPTORS causes ____ in the HEART
increase in contractile force
stimulation of ALPHA 1 RECEPTORS causes ____ in the VASCULAR SMOOTH MUSCLE
contraction –> arterial and venous vasoconstriction
What does PHENYLEPHRINE do?
pure alpha agonist –> increases peripheral arterial resistance and venous capacitance –> dose-dependent increase in BP –> baroreceptor-mediated increase in vagal tone –> decrease in heart rate
locations of alpha 2 receptors
postsynaptic CNS neurons platelets adrenergic and cholinergic nerve terminals some vascular smooth muscle fat cells
stimulation of ALPHA 2 RECEPTORS causes ____ in the PLATELETS
aggregation
stimulation of ALPHA 2 RECEPTORS causes ____ in the ADRENERGIC and CHOLINERGIC NERVE TERMINALS
inhibition of transmitter release
stimulation of ALPHA 2 RECEPTORS causes ____ in the VASCULAR SMOOTH MUSCLE
contraction
stimulation of ALPHA 2 RECEPTORS causes ____ in the FAT CELLS
inhibits lipolysis
SYSTEMIC administration of alpha 2 agonists do what
inhibit sympathetic tone and decrease BP
What is clonidine and what is it used for?
alpha 2 agonist, used to treat HTN
Where are the beta 1 receptors located?
heart
juxtaglomerular cells
Where are the beta 2 receptors located?
smooth muscle of respiratory system, uterus, vascular system
skeletal muscle
human liver
Where are the beta 3 receptors located?
bladder
fat cells
What does stimulation of Beta 1 receptors cause?
heart –> increased rate and contractile force
juxtaglomerular cells –> increased renin release
What does stimulation of Beta 2 receptors cause?
smooth muscle of respiratory system, uterus, vascular system –> muscle relaxation
skeletal muscle –> promotes uptake of potassium
human liver –> activates glycogenolysis
What does stimulation of Beta 3 receptors cause?
bladder –> relaxes detrusor muscle
fat cells –> activates lipolysis
What does ISOPROTERENOL do?
nonselective beta agonist that activates both beta 1 and beta 2
increases cardiac output due to increased contractility and direct SA node activation which increases heart rate
Where are the dobutamine receptors located?
D1: smooth muscle
D2: nerve endings
What does stimulation of Dopamine 1 receptors cause?
smooth muscle: dilates renal blood vessels
What does stimulation of Dopamine 2 receptors cause?
nerve endings: modulates neurotransmitter release
What does DOPAMINE do and what is it used for?
D1 receptor activation –> causes vasodilation; improves perfusion
What does DOPAMINE do in low vs high doses?
LOW: decreased peripheral resistance
HIGH: vasoconstriction due to activation of vascular alpha receptors
How do we deal with the vasoconstriction of DOPAMINE in high doses?
add DOBUTAMINE
What does DOBUTAMINE do?
beta 1 agonist
increase heart rate, contractility, and cardiac output to maintain renal perfusion
What effect does a beta 2 agonist have on the lungs?
bronchodilation to treat asthma
What effect does an alpha 2 agonist have on the eyes?
constricts “constrictor muscle” to improve flow of aqueous humor and decrease intraocular pressure for treatment of glaucoma
What effect does an alpha 1 agonist have on the genitourinary system?
contracts bladder base, urethral sphincter, and prostate to treat urinary incontinence
What effect does a beta agonist have on glucose, insulin, and metabolism?
increased lipolysis –> increased free fatty acids in the blood
increased insulin secretion from the pancreas
What effect does an alpha 2 agonist have on the pancreas?
decreased insulin secretion
What effect does alpha 1 agonism have on smooth muscle?
contraction of blood vessels, eye, bladder, prostate, uterus
What effect does alpha 1 agonism have on the liver?
glycogenolysis
What effect does alpha 1 agonism have on the salivary glands?
profuse secretion
What effect does a beta 1 agonist have?
increased heart rate and force as well as increased automaticity
What effect does a beta 2 agonist have?
smooth muscle relaxation
What effect does a beta 3 agonist have?
increased lipolysis
What do the indirect sympathomimetics do?
act by releasing previously-selected norephinephrine
What are some of the uses of indirect sympathomimetics?
ephedra: weight loss
phenylpropanolamine: appetite suppressant
AMPHETAMINES: CNS stimulants used to treat ADHD and narcolepsy
What is the risk of a sympathomimetic?
widespread and nonspecific effects which can impact the cardiovascular system
Most important effects to remember for sympathomimetics
alpha 1: most vascular smooth muscle; agonists CONTRACT
beta 1: heart; agonists INCREASE RATE
beta 2: respiratory and uterine smooth muscle; agonists RELAX
Which drugs activate both alpha and beta receptors?
EPINEPHRINE and NOREPINEPHRINE
Why is epinephrine and not norepinephrine used for the treatment of bronchospasm?
because epinephrine has a low affinity for beta 2, so is not as good at relaxing bronchial smooth muscle
What does EPINEPHRINE do?
primarily affects heart via beta 1 receptors; causes increase in heart rate, stroke volume, and cardiac output
What does NOREPINEPHRINE do?
vasoconstriction –> increases blood pressure –> reflex increase in parasympathetic output to heart, which slows the heart rate (happens DESPITE agonism of beta 1)
Effect of EPINEPHRINE on blood pressure
DOSE DEPENDENT
