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Pharmacology > Adrenergic Receptors 1 > Flashcards

Adrenergic Receptors 1 Flashcards

1
Q

Where does epinephrine originate? Where is its action?

A

The adrenal gland and from there it travels through the vasculature to distant organ effector sites

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2
Q

What class of compound is epinephrine? Norepinephrine?

A

Epi=Neurohormone; Norepi=Neurotransmitter

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3
Q

Where does norepinephrine metabolism occur?

A

In the liver and other distant sites

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4
Q

What two enzymes are critical for norepinephrine metabolism?

A

Catechol-o-methyl Transferase (COMT) and Monoamine Oxidase (MOA)

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5
Q

What are the four major activities of cholinergic and adrenergic synapses that can be pharmacologically modified?

A

Transmitter synthesis, Transmitter release, Receptor binding, and Termination

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6
Q

What drug can downregulate cholinergic transmitter synthesis?

A

HC-3; investigational/research only

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7
Q

What drug can downregulate adrenergic transmitter synthesis?

A

alpha-methyl tyrosine

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8
Q

What drug can downregulate cholinergic transmitter release?

A

Botulinus toxin

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9
Q

What drug can downregulate adrenergic transmitter release?

A

Bretylium

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10
Q

What drug can upregulate adrenergic transmitter release?

A

Amphetamine

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11
Q

What drug can downregulate cholinergic receptor binding?

A

Atropine

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12
Q

What drug can upregulate cholinergic receptor binding?

A

Methacholine

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13
Q

What drug can downregulate adrenergic receptor binding?

A

Propranolol

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14
Q

What drug can upregulate adrenergic receptor binding?

A

Isoproterenol

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15
Q

What drug can upregulate cholinergic termination?

A

Neostigmine

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16
Q

What drug can upregulate adrenergic termination?

A

Cocaine

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17
Q

What is the action of nerve gas?

A

Rampant upregulation of adrenergic termination

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18
Q

Where are B1 receptors found? What is their action?

A

Heart: increased heart rate and force of contraction; Kidney: Renin secretion

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19
Q

Where are B2 receptors found? What is their action?

A

Arterioles: Dilation; Bronchial smooth muscle: Relaxation; PG Uterus: Relaxation

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20
Q

Where are B3 receptors found? What is their action?

A

Adipose tissue, increasing lipolysis

21
Q

Where are a1 receptors found? What is their action?

A

Arterioles, Veins, Uterus, and Spleen: Constriction

22
Q

Where are a2 receptors found? What is their action?

A

Presynaptic: inhibit norepinephrine release; Postsynaptic (CNS only): decrease sympathetic tone

23
Q

Where are D1 receptors found? What is their action?

A

Renal, mesenteric, and cerebral arterioles: Dilation

24
Q

What major drugs have agonistic/antagonistic action on a1 receptors?

A

ag: Phenylephrine; antag: Prazosin

25
Q

What major drugs have agonistic/antagonistic action on a2 receptors?

A

ag: Clonidine; antag: Yohimbine

26
Q

What major drugs have agonistic/antagonistic action on D1 receptors?

A

ag: Fenoldopam (no antagonist)

27
Q

What major drugs have agonistic/antagonistic action on B1 receptors?

A

ag: Dobutamine; antag: Atenolol

28
Q

What major drugs have agonistic/antagonistic action on B2 receptors?

A

ag: Abuterol; antag: Butoxamine (would induce asthma)

29
Q

What major drugs have agonistic/antagonistic action on both B1 and B2 receptors?

A

ag: Isoproterenol; antag: Propranolol

30
Q

What is autoreceptor control in the context of norepinephrine and acetylcholine?

A

Self-regulation of neurotransmitter release by their own extracellular concentrations

31
Q

What is heteroreceptor control in the context of norepinephrine and acetylcholine?

A

Cross-talk between sympathetic and parasympathetic fibers where norepinephrine release from sympathetic fibers (i.e. those near vagus in the gut) that act on receptors on the parasympathetic fibers to reduce the release of acetylcholine. This is some of the mechanism of sympathetic:parasympathetic antagonism

32
Q

What surface phenotype allows vessels (especially in skeletal muscle) to both dilate and contract in the presence of varying doses of epinephrine?

A

The presence of a1 and B2 receptors mediates vasoconstriction and vasodilation. The B2 sensitivity threshold is lower, so it is most active at low epinephrine concentrations, stimulating vasodilation in fight-or-flight response. At high epinephrien concentrations, the a1 response predominates, mediting vasoconstriction (esp. in end-stage hempdynamic shock).

33
Q

What are the steps in neurotransmission (of norepinephrine)?

A

Uptake, Synthesis, Packaging, Action (calcium mediated), Release, Receptor interaction, and Termination

34
Q

What compounds are precursors to norepinephrine?

A

Tyrosine and Dopamine

35
Q

What is the distribution of alpha and beta receptor activity of the naturally occuring compounds? What molecular change affects this activity?

A

Norepinephrine is primarily alpha with B1 as well; epinephrine affects both receptor types; Isoproterenol affects beta receptors only; The more the terminal amine is sterically modified, the greater the beta selectivity. (NE=H, E=CH3, and IP=CH(CH3)2)

36
Q

What is the relationship in terms of receptor potency between norepinephrine and epinephrine?

A

Epinephrine is always more potent - by a little bit in most receptors, but dramatically more potent for B2 class

37
Q

What is the action of Tyramine? What class?

A

It bypasses calcium-mediated transmitter release to induce free, non-vesicular norepinephrine release and vasoconstriction; It is an indirect agonist

38
Q

What is the effect of repeat dosing of Tyramine?

A

Since it uses up free NE in the cytoplasm, repeat doses will have decreasing effects due to exhaustion of the limited pool of chemical available

39
Q

What is the type of activity that dopamine exerts on peripheral nerves?

A

Both direct and indirect; a release of cytoplasmic norepinephrine and a weak effect in the synaptic cleft

40
Q

What is the effect of hydroxylating dopamine?

A

C4-OH as in Tyramine allows indirect action, but C3-OH allows direct action

41
Q

What is the effect of low dose dopamine?

A

direct effect, especially on renal vessels to increase urine output

42
Q

What is the effect of medium dose dopamine?

A

Direct B1 activation with NE release to B1 and B2 receptors, increasing heart rate; indirect action is positively inotropic

43
Q

What is the effect of high dose dopamine?

A

a1 direct action, with some NE release; indirect action to induce vasoconstriction; can preserve kidney function following traumatic surgeries

44
Q

What is the effect of Fenoldopam?

A

Kidney protection by acting on dopamine receptors (D1) to increase renal bloodflow for a short time (t1/2 ~ 10 mintues)

45
Q

Why are the effect of norepinephrine dosing on heart rate in contrast to its effects on peripheral resistance/MAP? (EDIT LATER FOR ACCURACY)

A

Vagal/parasympathetic response is antagonistic to the sympathetic signaling and counteracts the low-level beta receptor activation - epinephrine is strong enough to counter this effect

46
Q

What are the major uses of alpha-1 agonists?

A

Control hemorrhage, local anasthetic, nasal decongestion, and anaphylactic shock

47
Q

What receptors need to be activated to counter anaphylactic shock?

A

alpha-1 and beta-2 (vasoconstriction and bronchodilation)

49
Q

What adrenergic receptor would you activate to treat hypotension?

A

alpha-1 to induce vasoconstriction

50
Q

List 4 compounds that would improve perfusion, especially of the kidneys?

A

Norepinephrine, Isoproterenol, Dopamine, and alpha-blockers

Pharmacology (5 decks)

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