Adrenergics I Flashcards
Dopamine is important in the regulation of:
Sodium excretion and renal function
Chemical structure of the catechol nucleus:
3,4 dihydroxyl benzene ring
Mechanisms of Indirect agonism:
1) Displacement and release of stored catecholamines
2) Inhibition of catecholamine reuptake
3) Blockade of metabolic enzymes
Differences in between non-catecholamines and catecholamines:
Less efficacious
Lipid soluble, penetrate the BBB (no OH)
Well absorbed orally
Longer duration of action (resistant to COMT)
MAO degradation of neurotransmitters occurs in the:
nerve terminal cytoplasm
MAO resistant neurotransmitter enter the nerve via this transporter:
Vesicular monoamine transporter (VMAT)
NE in the extra-synaptic space and circulating epinephrine are metabolized by:
COMT (Extraneuronal uptake)
The principal metabolite of norepinephrine in the brain:
3-hydroxy-4-methoxyphenyl glycol
The end-stage catecholamine metabolite ___ is excreted via the ____:
Vanilyllmandelic acid (VMA); urine
Stimulation of these alpha receptors leads to vasoconstriction:
Post-junctional Alpha-1 and Alpha-2
Stimulation of these alpha receptors leads to vasodilation:
Pre-junctional Alpha receptors
Endothelial Alpha-2
Beta-2 stimulation leads to ___ of muscle due to phosphorylation of ____:
relaxation; myosin light chain kinase (MLCK)
The dopamine receptors that stimulate adenylyl cyclase:
D1 and D5
Dopamine receptors inhibition adenylyl cyclase:
D2 (hyperpolarization)
D3 and D4
The most powerful stimulant of liver glycolysis:
Epinephrine
The most powerful stimulant of muscle glycolysis:
Isoproterenol
α1 > α2»_space;> β
Phenylephrine
Methoxamine
α2 > α1 »_space;> β
clonidine and methyldopa:
α1 = α2; β1»_space;> β2
Norepinephrine
α1 = α2; β1 = β2
epinephrine
β1 > β2»_space;> α
Dobutamine
β1 = β2»_space;> α
Isoproterenol
β2»_space; β1»_space;> α
terbutaline and albuterol
D1 = D2»_space; β»_space; α
Dopamine
D1»_space; D2
Fenoldopam
Best choice for cardiogenic shock:
Dopamine
Tachyphylaxis desensitization is exemplified by:
indirectly acting sympathomimetic drugs
Two categories of GPCR mediated desensitization:
Homologous (arrestin)
Heterologous (phosphorylation)
The parent compound of catecholamines, ___, is composed of:
phenylethylamine; benzene ring + ethylamine with terminal amino group
Dopamine structure is a catechol nucleus + ___:
ethylamine
Norepinephrine structure is dopamine + ___:
OH at β-carbon
Epinephrine structure is norepinephrine + ___:
methyl group at amino terminal
Isoproterenol structure is epinephrine + ___:
2 methyl groups at methyl substitution
in catecholamines, the larger the ___ substitution, the greater the affinity to __ receptors:
alkyl; β receptors
Phenylephrine is epinephrine structure without the ____:
1 OH group on benzene ring
Ephedrine has these differences from epinephrine structure:
less 2 OH groups
Methyl-substitution on the α-carbon
Absence of this group makes non-catecholamines resistant to COMT:
OH groups
Presence of this group makes non-catecholamines resistant to MAO:
α-carbon methyl group
As size of amino group substituents increases:
Increased β receptor activity
Decreased α receptor activity
Groups with substitution to the α-carbon block ___ metabolism and act ___:
MAO; indirectly
Groups with substitution to the β-carbon act ___ and may be important in the ___:
Directly; storage of transmitters in neural vesicles
Tissues with α1 receptors:
Most vascular smooth muscle
Pupillary dilator muscle
Pilomotor smooth muscle
Heart
Tissues with α2 receptors:
Postsynaptic CNS adrenoreceptors Platelets Adrenergic and cholinergic nerve terminals Vascular smooth muscle Fat cells JG cells
Tissues with β2 receptors:
Respiratory, uterine and vascular smooth muscle
Skeletal muscle
Human liver
Use of pure α agonists lead to this cardiovascular reflex:
Reflex bradycardia
Receptors for decreased insulin secretion:
α2
Receptors for increased insulin secretion:
β
These receptors stimulate renin secretion:
β1
These receptors inhibit renin secretion:
α2
Adrenoreceptors modulate the secretion of:
PTH
Calcitonin
Thyroxine
Gastrin
In high concentrations, Epi and others cause:
Leukocytosis
At high doses of epinephrine __ receptors are more sensitive, but __ receptor effects predominate, leading to a ____ response:
β2 (decreased DP); α (increased DP); biphasic
Chief vascular action of epinephrine is on the components:
Smaller arterioles
Precapillary sphincters
Metabolic effects of epinephrine:
Hyperglycemia
Hyperlipediemia
Increased calorigenic action
Hypokalemia
___ is CI in pregnant women due to it’s lack of ___ receptor sensitivity:
Norepinephrine; β2
Adverse effects associated with epinephrine:
Cerebral hemorrhage (α1 BP effects) Cardiac arrythymias (β1) Skeletal muscle tremors (β2)
Therapeutic uses of epinephrine:
Anaphylactic shock Prolong local anesthetics Control of hemorrhage Cardiac arrest Chronic angle glaucoma Acute bronchial asthma
CI for epinephrine:
Patients on non-selective beta blockers
Patients with CAD
Unlike epinephrine, norepinephrine is associated with reflex _____:
bradycardia (no β2 effects leads to tremendous BP increase)
Locked-lung syndrome:
Congestion of the bronchial mucosa caused by repeated administration is isoproterenol
Major use of dopamine:
Chronic refractory congestive heart failure
Dobutamine substitutes an ___ group in place of the amino group and is a ____ receptor agonist:
aromatic; dopamine and β1
The effect of dobutamine is more on ____ than on ____:
myocardial contraction (inotropic); heart rate (chronotropic)
CI of dobutamine:
Idiopathic hypertrophic subaortic stenosis
Therapeutic uses of phenylephrine:
Topical nasal decongestant
Mydriatic (increase pupillary size)
Vasopressor drug
Paroxysmal supraventricular tachycardia
Rebound congestion is minimal if:
The drug is taken orally
Ephedrine has a receptor sensitivity profile identical to ___:
Epinephrine
Ephedrine has this mode of action:
Direct and Indirect
Amphetamine is an ____ acting agent increasing ____ release and duration:
indirectly; norepinephrine
Therapeutic uses of amphetamine:
ADHD
Narcolepsy
Obesity
Terbutaline is a ___ agonist and not easily metabolized by___:
β2; COMT
Clonidine is a ____ agonist associated with ____ when discontinued suddenly:
α2; rebound hypertension (sympathetic compensation)
General CI when using adrenergic drugs:
Hypertension Cerebral arteriosclerosis Hyperthyroidism Acute coronary disease Diabetes BPH Narrow angle glaucoma
α2 selective drugs have _____ effects:
Sympathetic depressant
α2 selective drugs used in wide angle glaucoma:
Apraclonidine
Brimonidine