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Flashcards in Adrenergic Drugs Deck (128)
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1

Synthesis of NT in Adrenergic nerve terminal

1. tyrpsine is actively transported into nerve endings
2. is converted into DOPA by tyrosine hydroxyls (Rate-limiting step)
3. DOPA is converted to dopamine by DOPA decarboxylase
4. DA is metabolized to NE via Dopamine beta decarboxylase
5. NE is taken up & stored in granules; NE not stored in granules is called the mobile pool--this can be inactivated by MAO

During depolarization, Ca2+ enters the presynaptic terminal via the voltage-dependent Ca channels-->degranulation of storage vesicles-->NE released via exocytosis into synaptic junction

Actions:
1. NE can activate pre junctional receptors = alpha 2 receptors (feedback regulation system-->inhibition of further release)
2. can activate postsynaptic receptors (alpha 1 & beta 1-3 receptors)

2

Termination of NE action

1. mainly by reuptake (via NET= NE transporter)
2. Diffusion away from receptor site with eventual metal by catechol-o-methyl transferase (COMT) in plasma or liver

3

MAO inhibitors

increase the pre junctional levels of NE

4

Displacers

indirect acting sympathomimetics displace the stored NE

5

uptake inhibitors

indirect actinv sympathomimetics inhibit the uptake into nerve cell-->increases post junctional levels/actions of NE

6

alpha 2 receptor

pre-synaptic autoreceptor

coupled to G2-->inhibition of adenyl cyclase-->decrease cAMP

7

D1 receptors

activates adenyl cyclase-->increases cAMP

8

alpha 1 receptors

coupled to Gq-->stimulates PLC-->activates IP3 & DAG pathway

9

beta receptors

coupled to Gs-->activation of adenyl cyclase-->increased cAMP

10

Things that affect PVR

alpha 1: vasoconstriction-->increase TPR-->Increase BP

beta 2: vasodilation-->decrease TPR-->decrease diastolic BP

11

alpha 1 receptor locations & actions

1. most vascular smooth muscle-->vasoconstriction--> Increase TPR & Increase BP
2. Pupillary dilator muscle-->contraction-->dilates pupil
3. Prostate (ductus deferens & seminal vesicles)--> contraction-->ejaculation

12

alpha 2 receptor locations & actions

1. postsynaptic CNS adrenoceptors-->probably multiple
2. presynaptic nerve terminals-->inhibition of NT release--> decrease sympathetic outflow
3. some vascular smooth muscle (nasal mucosa)--> nasal decongestion
4. fat cells--> inhibition of lipolysis

13

beta 1 receptor locations & actions

1. heart--> increase F & rate of contraction
2. juxtaglomerular cells--> increase renin release

14

beta 2 receptor locations & actions

1. bronchial relaxation-->bronchodilation
2. uterine relaxation
3. vascular bed in skeletal muscle

vasodilation-->decrease TPR
4. skeletal muscle-->promotes K uptake
5. human liver-->activates glycogenolysis
6. increase pancreas insulin secretion

15

beta 3 receptor locations & actions

Fat cells-->activates lipolysis

16

D1 receptor locations & actions

dilates renal bv

17

D2 receptor locations & actions

nerve endings--> modulates NT release

18

Indirect agonist types:

1. act via displacement of stored catecholamines from adrenergic nerve ending
ex) amphetamine & tyramine

2. act via inhibition of repute of catecholamines already released
ex)cocaine & TCAs

some drugs may have direct & indirect actions

19

Indirect acting adrenergic agonists

1. tyramine
2. amphetamine
3. ephedrine*
4. metaraminol*
1-4 increase release of NE
5. cocaine (blocks reuptake

20

Nonspecific Adrenergic Agonists

1. NE: a1=a2, B1>>B2
2. Epi: a1=a2=b1=b2
3. Dopamine: D1=D2>B1>>a
4. Ephedrine: a1=a2=b1=b2

21

a1=a2=b1=b2

Epi & Ephedrine

22

alpha 1 agonists

1. phenylephrine
2. methoxamine
3. metaraminol

23

alpha 2 agonists

clonidine

24

non-specific beta agonists

isoproterenol; B1=B2

25

beta 1 agonists

dobutamine

26

beta 2 agonists

1. terbutaline*
2. albuterol*
3. metaproterenol
4. ritodrine*

27

NE

non-specific adrenergic agonist: a1=a2; B1>>B2

28

Fendolopam

D1 agonist

29

Adrenergic effect on BV
a1 -->
B2-->

a1--> increases arterial resistance
b2-->promote sm relaxation-->decrease arterial resistance

skin & splanchnic vessels have predominantly alpha receptors & constrict in the presence of Epi & NE

30

Adrenergic effect on Heart

1. direct effects via B1 receptors-->increased Ca influx into cardiac cells = Pacemaker activity increased (+ chronotropic effect)
2. conduction velocity in AV node increased
3. intrinsic contractility is increased (+ inotropic effect)