PHL 313 Lab 3 2 3 Adrenergic Receptors α 1 receptor vasoconstriction blood pressure α 2 receptor inhibit release of norepinephrine negative feedback 4 β 1 receptor ID: 920954
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1
Effect of adrenergic drugs on intestine and identification of unknown.
PHL 313 Lab
.
3
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Adrenergic Receptors
α
1
receptor
vasoconstriction
blood pressure
α
2
receptor
inhibit release of
(nor-epinephrine)
negative feed-back
Slide44
β1 receptor
heart rate
Force of contraction
Adrenergic Receptors
β
2
receptor
vasodilatation
bronchodilatation
glycogenolysis release of glucagons
Slide55
Slide6Catecholamines They are sympathetic hormonesThey are released by the adrenal glands in response to stressThey are part of sympathetic nervous system
They contain a catechol group and amino acid tyrosin6
Slide7Production and degradationCatecholamines are produced mainly by the chromaffin cells of the adrenal medulla and postsganglionic fibers of sympathetic nervus system.
Dopmaine is the first catecholamine to be synethesied. Ep. And NE are createdand modified from dopamine.Tyrosin is created from phenylalanine by hydroxylation by enzyme phenylalanine hydroxylase.7
Slide8Catecholamine synthesis is inhibited by alpha- methyl-p- tyrosine (AMPT) which inhibits tyrosine hydroxylase.
8
Slide9Catecholamines degradationCatecholamines have a half- life of a few minutes when circulating in blood.
They are degraded by COMT or MAO.Amphetamines and MAOIs bind to MAO in order to inhibit its action of breaking down catecholamines.This is the primary reason why the effects of amphetamines have a longer lifspan than cocaine and other substances
9
Slide10Amphetamines not only cause a rlease of dopamine, ep,and NE into blood stream but also supress re- absorption.Two catcholamines,NE and dopamine act as neuromodulators in CNS and as hormones in blood circulation.
High catecholamine level in blood are associated with stress.10
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Antagonists
Agonists
Mechanism
Selected action
of agonist
Agonist potency order
Receptor type
α1 blockers
Alfuzosin
Doxazosin
Phentolamine
Prazosin
Tamsulosin
Terazosin
α1 agonists
norepinephrine
Phenylephrine
Methoxamine
Cirazoline
G
q
: phospholipase C (PLC) activated, IP
3
and calcium up
smooth muscle contraction
norepinephrine ≥ epinephrine >>
isoprenaline
α
1
:
α2
blockers
Yohimbine
Idazoxan
α2 agonists
Clonidine
Lofexidine
Xylazine
Tizanidine
Gi: adenylate cyclase inactivated, cAMP down
smooth muscle contraction and neurotransmitter inhibition
norepinephrine ≥ epinephrine >>
isoprenaline
α2
:
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Antagonists
Agonists
Mechanism
Selected action
of agonist
Agonist potency order
Receptor type
(Beta blockers)
Metoprolol
Atenolol
Propranolol
norepinephrine
Isoprenaline
Dobutamine
G
s
: adenylate cyclase activated, cAMP up
heart muscle contraction
isoprenaline
> epinephrine = norepinephrine
β
1
(Beta blockers)
Propranolol
Short/long)
Salbutamol
Formoterol
Isoprenaline
Salmeterol
Terbutaline
G
s
:
adenylate
cyclase
activated,
cAMP
up
smooth muscle relaxation
isoprenaline
> epinephrine >> norepinephrine
β2
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Identification of unknown
1-
0.2ml of
Unknown
, record & wash
2-
0.2ml
of C
6
- blocker, leave 2 min.
without wash add 0.2ml of Unknown, if (1) block so unknown is nicotine-like drug but if unknown gives a response
so the unknown may be muscarinic or
direct acting- like drug.3- If unknown gives a response wash and continue4- 0.2ml of atropine , leave 2 min. without wash add 0.2ml of of unknown , if block, so the unknown is muscarin
-like drug
but if unknown gives a response so it is
direct acting- like drug.