Adrenergic receptors Dr S Parthasarathy MD DA DNB MD Acu Dip DiabDCA Dip Software statistics Ph d Mahatma Gandhi Medical college and research institute puducherry ID: 763108
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Adrenergic receptors Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab.DCA, Dip. Software statistics- Ph dMahatma 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 α 1 α 2β 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 α 1Smooth 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 (renal, mesenteric causing possible constriction).
Alpha receptors Noradrenaline > adrenaline > > isoprenalinebeta receptorsIsoprenaline > adrenaline > noradrenaline
Pharmacological dynamism After stoppage of beta blockers , there is sudden increase of beta receptors
Adrenergic agonists Alpha Beta Alpha 1Alpha 2Beta 1 Beta 2 Beta 3 Adrenaline Noradrenaline Phenyleph Clonidine Dobutamine Terbutalin Isoprenaline norad Oxymetazoline Dopamine Dopamin e Ephedrine Ephedrine
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 dyspnoeaAdrenaline
Why we should use adrenaline AdditivesCPR
Ephedrine Direct B1 and B 2 and indirect alpha 1May cause tachycardia and hypertensionIdeal 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 atropineActs on b1 and b2 receptorsIsoprenaline
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 betaInotropy 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 dobutamineAdrenaline 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 Alpha Beta Alpha 1Alpha 2Beta 1 Beta 2 Beta 3 Adrenaline Noradrenaline Phenyleph Clonidine Dobutamine Terbutalin Isoprenaline norad Oxymetazoline Dopamine Dopamin e Ephedrine Ephedrine
Blockers Alpha Beta Alpha 1Alpha 2Beta 1Beta 2 Beta 3 labetolol labetolol Phent , phenoxy propranolol Prazosin Yohimbine Aten Butoxami Tamsulosin
Thank you