ADRENERGIC RECEPTORS
Dr. S. Parthasarathy
MD., DA., DNB, MD (Acu),
Dip. Diab.DCA, Dip. Software statistics- Ph d
Mahatma Gandhi Medical college and research
institute , puducherry , India
AHLQUIST – 1948
PROGRESS
ADRENERGIC RECEPTORS
WHAT IS THIS ??
 Two transmitters
 Adrenaline
 Acetyl choline


Its noradrenaline
CLASSIFICATION

α


α1
α2
β



β1
β2
β3
MOST OF THE DRUGS ACT ON SOME OTHER
RECEPTORS ALSO

Dopamine
DA 1
 DA 2

ALPHA RECEPTORS
ALPHA RECEPTORS
Vasoconstriction
 Metabolism
 Conscious status
 Nociception

ALPHA RECEPTORS
α1
 Smooth vessels of blood vessels
 Vasoconstriction

Liver – glycogenolysis
 Intestine – contraction

ALPHA 1 AGONISTS – MINOR






mydriasis (pupillary dilation due to contraction
of the radial eye muscles),
broncho constriction,
uterine contracture,
contraction of sphincters in the gastrointestinal and
genitourinary tracts.
α 1-Stimulation also inhibits insulin secretion and
lipolysis.
α 1-receptors that have slightly positive inotropic and
negative chronotropic effects
ALPHA 2

Platelet aggregation

Sympathetic nerve endings

Decrease norad release

Pancreatic beta cell

Decrease insulin release
BETA
BETA 1

Heart – force , rate, excitability increased

Renal JG apparatus - ↑ rennin release
BETA 2

Smooth muscle of bronchi, blood vessel, uterus
bladder-

vasodilation and relaxation

Heart – force, rate increased

Skeletal muscle – hypokalemia

Beta cell pancreas- ↑ insulin
BETA 3

Fat – thermogenesis
Subcutaneous tissue

Lipolysis

DOPAMINE

Dopamine-1:

vascular smooth muscle (renal, mesentery, coronary causing
vasodilation),renal tubules
(natriuresis, diuresis),

juxtaglomerular cells (increased renin release).

Dopamine-2:

postganglionic sympathetic nerves (inhibits NE release),
smooth
muscle
constriction).
(renal,
mesenteric
causing
possible
ALPHA RECEPTORS

Noradrenaline > adrenaline > > isoprenaline
beta receptors
 Isoprenaline > adrenaline > noradrenaline

PHARMACOLOGICAL DYNAMISM

After stoppage of beta blockers , there is
sudden increase of beta receptors
ADRENERGIC AGONISTS
Dopamine
Phenyleph
Dopamine
Clonidine
Dobutamine
Isoprenaline
Oxymetazoline
Noradrenaline
Terbutalin
norad
Adrenaline
Alpha
Alpha 1
Ephedrine
Beta
Alpha 2
Beta 1
Beta 2
Ephedrine
Beta 3
DIFFERENCES
Adrenaline , noradrenaline and dopamine –
 Natural catecholamines


Direct acting and indirect acting
SUMMARY

Alpha 1

Alpha 2

Beta 1

Beta 2
ANAPHYLAXIS
alpha-adrenergic receptors,
_____lessens the vasodilation and
increased vascular permeability.
action on beta- receptors,
________causes bronchial
smooth muscle relaxation that helps
alleviate bronchospasm, wheezing,
and dyspnoea

Adrenaline
WHY WE SHOULD USE ADRENALINE

Additives

CPR
EPHEDRINE
Direct B1 and B 2 and indirect alpha 1
 May cause tachycardia and hypertension


Ideal for spinal epidural hypotension especially
in pregnant patients- should not cross placenta
CARDIOGENIC SHOCK.

Dobutamine
Acts on b1 and b2, with minimal action on a1
receptors.
 It increases cardiac output and reduces
afterload (b2effects on skeletal muscle).

SEPTIC SHOCK
Vasodilation is predominant pathology
 Inotrope with minimal beta 2 action

Use noradrenaline
 Sys, dias, MAP increase without CO increase
No chronotropic effects

ISOPRENALINE

Complete heart block, overdose of beta blocker
or severe bradycardia unresponsive to atropine

Acts on b1 and b2 receptors

Isoprenaline
CARDIOGENIC SHOCK WITH OLIGURIA

Beta 1, alpha 1 and DA 1 and DA 2

Dopamine
2 µg / kg
 5 µg / kg
 10 µg / kg

DOBUTAMINE

Alpha and beta

Inotropy with minimal vasodilation at low doses
But alpha vasoconstriction predominates in higher
doses
 Increases myocardial oxygen consumption – stress
testing
 Use in patients where myocardial O2 consumption
??

Sudden hypotension and aortic stenosis
 obstructive hypertrophic cardiomyopathy,


Phenylephrine

Nitrates and viagra induced BP fall
ACUTE MI

Dopamine and dobutamine individual or
combination

Vasopressin

RV infarct – IV fluids and dobutamine
POST CARDIAC SURGERY STATUS

Correction of the cause with dobutamine

Adrenaline

Isoprenaline where we need the highest kick
and not bother about tachycardia
BRONCHIAL ASTHMA

We want only beta 2 agonists

Terbutaline and others
CLONIDINE

Adrenergic receptor agonist
But hypotension
 Analgesia
 Sedation


Alpha 2 agonist
RITODRINE , ISOXSUPRINE

Preterm labour

Beta 2 agonist
Not much tachycardia
 not much hypotension

ADRENERGIC AGONISTS
Dopamine
Phenyleph
Dopamine
Clonidine
Dobutamine
Isoprenaline
Oxymetazoline
Noradrenaline
Terbutalin
norad
Adrenaline
Alpha
Alpha 1
Ephedrine
Beta
Alpha 2
Beta 1
Beta 2
Ephedrine
Beta 3
BLOCKERS
Beta
Alpha
Alpha 1
Alpha 2
labetolol
Tamsulo
sin
Beta 2
labetolol
Phent, phenoxy
Prazosin
Beta 1
Yohimbine
propranolol
Aten
Butoxami
Beta 3
THANK YOU