Adrenergic Drugs Flashcards
(128 cards)
Synthesis of NT in Adrenergic nerve terminal
- tyrpsine is actively transported into nerve endings
- is converted into DOPA by tyrosine hydroxyls (Rate-limiting step)
- DOPA is converted to dopamine by DOPA decarboxylase
- DA is metabolized to NE via Dopamine beta decarboxylase
- 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:
- NE can activate pre junctional receptors = alpha 2 receptors (feedback regulation system–>inhibition of further release)
- can activate postsynaptic receptors (alpha 1 & beta 1-3 receptors)
Termination of NE action
- 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
MAO inhibitors
increase the pre junctional levels of NE
Displacers
indirect acting sympathomimetics displace the stored NE
uptake inhibitors
indirect actinv sympathomimetics inhibit the uptake into nerve cell–>increases post junctional levels/actions of NE
alpha 2 receptor
pre-synaptic autoreceptor
coupled to G2–>inhibition of adenyl cyclase–>decrease cAMP
D1 receptors
activates adenyl cyclase–>increases cAMP
alpha 1 receptors
coupled to Gq–>stimulates PLC–>activates IP3 & DAG pathway
beta receptors
coupled to Gs–>activation of adenyl cyclase–>increased cAMP
Things that affect PVR
alpha 1: vasoconstriction–>increase TPR–>Increase BP
beta 2: vasodilation–>decrease TPR–>decrease diastolic BP
alpha 1 receptor locations & actions
- most vascular smooth muscle–>vasoconstriction–> Increase TPR & Increase BP
- Pupillary dilator muscle–>contraction–>dilates pupil
- Prostate (ductus deferens & seminal vesicles)–> contraction–>ejaculation
alpha 2 receptor locations & actions
- postsynaptic CNS adrenoceptors–>probably multiple
- presynaptic nerve terminals–>inhibition of NT release–> decrease sympathetic outflow
- some vascular smooth muscle (nasal mucosa)–> nasal decongestion
- fat cells–> inhibition of lipolysis
beta 1 receptor locations & actions
- heart–> increase F & rate of contraction
2. juxtaglomerular cells–> increase renin release
beta 2 receptor locations & actions
- bronchial relaxation–>bronchodilation
- uterine relaxation
- vascular bed in skeletal muscle
vasodilation–>decrease TPR
- skeletal muscle–>promotes K uptake
- human liver–>activates glycogenolysis
- increase pancreas insulin secretion
beta 3 receptor locations & actions
Fat cells–>activates lipolysis
D1 receptor locations & actions
dilates renal bv
D2 receptor locations & actions
nerve endings–> modulates NT release
Indirect agonist types:
- act via displacement of stored catecholamines from adrenergic nerve ending
ex) amphetamine & tyramine - act via inhibition of repute of catecholamines already released
ex) cocaine & TCAs
some drugs may have direct & indirect actions
Indirect acting adrenergic agonists
- tyramine
- amphetamine
- ephedrine*
- metaraminol*
1-4 increase release of NE - cocaine (blocks reuptake
Nonspecific Adrenergic Agonists
- NE: a1=a2, B1»B2
- Epi: a1=a2=b1=b2
- Dopamine: D1=D2>B1»a
- Ephedrine: a1=a2=b1=b2
a1=a2=b1=b2
Epi & Ephedrine
alpha 1 agonists
- phenylephrine
- methoxamine
- metaraminol
alpha 2 agonists
clonidine
non-specific beta agonists
isoproterenol; B1=B2