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ADRENERGIC RECEPTORS AND 
MODULATORS 
Dr Imran Zaheer 
JNMCH, AMU 
Aligarh
INTRODUCTION
Sympathetic System 
 Preganglionic fibers originate 
from 
• Thoracic (T1-T12) 
segments of the cord 
• Lumbar (L1-L3) 
segments of the cord 
 Most of the ganglia are 
located in paravertebral 
chains that lie along the spinal 
cord 
 Few (prevertebral) on the 
anterior aspect of the aorta 
 Preganglionic fibers are short 
and the postganglionic fibers 
are long
NEUROTRANSMITTERS 
• 3 types Collectively called catecholamines 
1. Noradrenaline(NA)at postganglionic sympathetic sites(except 
sweat glands, hair follicles) & in certain areas of brain. 
2. Adrenaline(Adr)secreted by adrenal medulla 
3. Dopamine(DA)transmitter in basal ganglia, limbic system, CTZ, 
anterior pituitary.
occurs in 
adrenergic 
neuronal 
cytoplasm 
occurs inside 
granules 
occurs in 
adrenal 
medulla
STORAGE OF TRANSMITTER 
• Stored in synaptic vesicles or granules within adrenergic nerve 
terminal. 
• Vesicular membrane actively takes DA from cytoplasm & synthesize 
NA inside vesicle with help of DA β-hydroxylase. 
• NA stored in a complex with ATP(4:1) adsorbed on protein 
chromogranin A. 
• In adrenal medulla, NA thus formed is diffuses into cytoplasm 
where it is methylated to Adr. 
• Adr so formed is stored in separate granule  Chromaffin granule.
RELEASE OF TRANSMITTER 
• Depolarisation of nerve terminal 
membrane opens calcium 
channels in nerve terminal 
membrane & resulting entry of 
Ca2+ promoting fusion and 
discharge of synaptic vesicles
REGULATION OF TRANSMITTER RELEASE 
• Release of cotransmitters can be 
modulated by prejunctional 
autoreceptors and 
heteroreceptors. 
• Following their release from 
sympathetic terminals, all three 
cotransmitter norepinephrine, 
neuropeptide Y (NPY), and ATP 
can feedback on prejunctional 
receptors to inhibit the release of 
each other. 
• Enhancement of sympathetic 
neurotransmitter release can be 
produced by activation of b2 
adrenergic receptors
UPTAKE OF NEUROTRANSMITTER 
Transport of 
noradrenaline 
Uptake 1 
(Norepinephrine 
Transporter) 
Uptake 2 
(Extraneuronal 
amine Transporter) 
Vasicular Transporter 
(VMAT- 2) 
Specificity NA > A A > NA NA = A 
Location Neuronal membrane Non-neuronal cell 
membrane (smooth 
muscle, cardiac 
muscle, endothelium) 
Synaptic vesicle 
membrane 
Other substrates Tyramine 
guanethidine 
(+)-Noradrenaline 
Histamine 
Dopamine 
5-HT 
Inhibitors Cocaine 
Tricyclic 
Antidepressants (e.g. 
desipramine 
Steroid hormones 
(e.g. corticosterone) 
Phenoxybenzamine 
Reserpine
Metabolism of neurotransmitter 
• Endogenous & exogenous catecholamines are metabolised mainly 
by two enzymes, monoamine oxidase & catechol-O-methyl 
transferase (COMT). 
• MAO occurs within cells bound to surface membrane of 
mitochondria, abundant in noradrenergic nerve terminals. 
• COMT a widespread enzyme that occurs in both neuronal and non-neuronal 
tissues, acts on both catecholamines & its deaminated 
products, produced by action of MAO. 
• Main final metabolite of adrenaline & noradrenaline is 3-methoxy- 
4-hydroxymandelic acid (VMA).
DEAMINATION DEAMINATION 
ALDEHYDE 
DEHYROGENASE 
ALDEHYDE 
REDUCTASE 
3,4-DIHYDROXYPHENYL GLYCOL 3,4-DIHYDROXYMANDELIC ACID 
3-METHYL,4-HYDROXYPHENYLGLYCOL 
ALCOHOL DEHYROGENASE 
ALDEHYDE 
DEHYROGENASE 
VANILLYL MANDELIC ACID
ADRENERGIC RECEPTORS 
• All belong to superfamily of G-protein-coupled receptors
α1 α2 β1 β2 β3 
Second 
messengers 
and effectors 
PLC activation ↓cAMP ↑cAMP ↑cAMP ↑cAMP 
↑ IP3 
↑DAG 
↑Ca2+ 
Selective 
agonists 
Phenylephrine, 
methoxamine 
Clonidine, 
clenbuterol 
Dobutamine, 
xamoterol 
Salbutamol, 
terbutaline, 
salmeterol, 
formoterol 
BRL 37344 
Selective 
antagonists 
Prazosin, 
doxazocin 
Yohimbine, 
idazoxan 
Atenolol, 
metoprolol 
Butoxamine
Effects of receptor activation 
Tissues and 
effects α1 α2 β1 β2 β3 
Blood vessels Constrict Constrict Dilate 
Bronchi Constrict Dilate 
GI tract Relax Relax 
(presynaptic 
effect) 
Relax 
GI sphincters Contract 
Uterus Contract Relax 
Bladder 
Relax 
detrusor
α1 α2 Β1 Β2 β3 
Bladder 
sphincter 
Contract 
Seminal tract Contract Relax 
Iris (radial 
muscle) 
Contract 
Ciliary 
muscle 
Relax 
Heart: 
Rate Increase 
Force of 
Increase 
contraction
α1 α2 β1 β2 β3 
Liver Glycogenolysis Glycogenolysis 
Fat Lipolysis 
Thermogenesis 
Pancreatic 
islets 
Decrease 
insulin 
secretion
α1 α2 β1 β2 β3 
Nerve 
Terminal: 
Adrenergic Decrease 
release 
Increase 
release 
Cholinergic Decrease 
release 
Salivary 
gland 
K+ release 
and watery 
secretion 
Amylase 
secretion 
Mast cells Inhibition of 
histamine 
release
Receptor Regulation 
• Responses mediated by adrenoceptors are not constantly same. 
• Three processes have considerable clinical significances. 
1. Desensitisation 
2. Up – Down regulation 
3. supersensitivity
DRUGS THAT AFFECT ADRENERGIC RECEPTOR
DRUGS THAT AFFECT ADRENERGIC NEURONS
Therapeutic Classification of Adrenergic Drugs 
• Pressure agents 
Noradrenaline Ephedrin Dopamine Phenylephrine Methoxamine 
• Cardiac stimulants 
Adrenalin Dobutamine Isoprenaline 
• Bronchodilators 
Isoprenal Salbutamol Salmeterol Formoterol 
• Nasal Decongestants 
Phenylephrine Xylometazoline Oxymetazoline Naphazoline 
• CNS Stimulants 
Amphetamine Methamphetamine Dexamphetamine 
• Anorectics 
Fenfluramine Sibutramine Dexfluramine 
• Uterine relanxant & vasodilators 
Ritodrine Isoxsuprine Salbutamol Terbutaline
Clinical uses of adrenoceptor agonists 
• Cardiovascular system 
– cardiac arrest: adrenaline 
– cardiogenic shock: dobutamine (β1-agonist) 
– heart block: β-agonists (e.g. isoprenaline) can be used temporarily 
while electrical pacing is being arrange 
• Anaphylactic shock (acute hypersensitivity) 
– adrenaline is the first-line treatment along with steroids & 
antihistaminics 
• Respiratory system 
– Asthma : selective β2-receptor agonists (salbutamol, terbutaline, 
salmeterol, formoterol) 
– nasal decongestion: drops containing oxymetazoline or ephedrine for 
short-term use
• Miscellaneous indications 
– adrenaline can be used to prolong local anaesthetic action 
– miscellaneous indication for α2-agonists (e.g. clonidine) include 
hypertension , menopausal flushing, lowering intraocular 
pressure & migraine prophylaxis 
– Obesity 
– CNS uses 
• Hyperkinetic children 
• Narcolepsy
TOXICITY OF ADRENERGIC DRUGS 
• Restlessness, palpitation, anxiety, tremor, may occur after s.c. /i.m. 
injection of Adr. 
• Marked rise in BP leading to cerebral haemorrhage. 
• Ventricular tachycardia/fibrillation, angina, myocardial infarction are 
the hazards of large doses of Adr. 
• CNS toxicity is rarely observed with adr. drugs 
– In moderate doses, amphetamines commonly cause 
restlessness, tremor, insomnia, & anxiety; in high doses, a 
paranoid state may be induced.
ADRENERGIC ANTAGONISTS 
• These are drugs which antagonize the receptor action of adrenaline 
and related drugs. 
• They are competitive antagonists at α or β or both α and β. 
1. α ADRENERGIC BLOCKING DRUGS 
2. β ADRENERGIC BLOCKING DRUGS
α ADRENERGIC BLOCKING DRUGS 
I. Nonequilibrium type 
 B-Haloalkylamines - Phenoxybenzamine. 
ll. Equilibrium type 
A. Nonselective 
(i) Ergot alkaloids-Ergotamine, Ergotoxine 
(ii) Hydrogenated ergot alkalolds-Dihydroergotamine(DHE), Dihydroergotoxine 
(iii) Imidazolines-- Phentolamine 
(iv) Miscellaneous - Chlorpromazine 
B. α1 selective- Prazosin, Terazosin, Doxazosin, Tamsulosin 
C. α2 selective- Yohimbine
Pharmacological properties 
 Cardiovascular effect 
• Blockade of α receptors → vasodilatation → decrease in peripheral 
vascular resistance → fall in BP → Hypotension. 
• Resultant fall in BP → baroreceptor reflex → sympathetic discharge since 
α receptors are blocked, stimulates β1 receptor in heart → tachycardia 
• α receptors blocked → absence of efficient peripheral vasoconstriction in 
erect posture → peripheral pooling of blood → cerebral hypoxia , vertigo 
and fainting → postural hypotension
• Nasal stuffiness due to blocked of α receptor in nasal blood vessels. 
• Miosis due to loss of tone of radial muscles of iris. 
• Tone of smooth muscle in bladder trigone, sphincter and prostate 
is reduced by blockade of α1 receptor → urine flow in patients with 
benign hypertrophy of prostate (BHP) is improved. 
• Inhibition of contractions of vas deferens and ejaculatory duct → 
failure of ejaculation → impotence 
• Intestinal motility is increased due to partial inhibition of relaxant 
sympathetic influences → diarrhoea
β ADRENERGIC BLOCKING DRUGS 
Nonselective (β1 and β2 ) 
a. Without intrinsic sympathomimetic activity 
Propranolol, Sotalol, Timolol. 
b. With intrinsic sympathomimetic activity 
Pindolol 
c. With additional α blocking property 
Labetalol, Carvedilol 
Cardioselective (β1) 
Metoprolol, Atenolol, Acebutolol, Bisoprolol 
Esmolol, Betaxolol, Celiprolol, Nebivolol
Classifying B blockers into 3 generations
Pharmacological properties 
Cardiovascular system 
• ↓ heart rate, ↓ myocardial contractility, ↓ conduction velocity,↓ 
myocardial oxygen demand 
Though β1 receptor blockade is the main mechanism responsible 
for antihypertensive effect : 
- ↓ renin release 
- ↓ decrease in central sympathetic outflow 
- Chronic ↓ in c.o 
- Blockade of facilitatory effect of presynaptic β2 receptor on 
NE release.
Pulmonary system 
– Least affect on bronchial muscle of normal individuals. 
– In asthmatic or COPD pts→ severe bronchoconstriction. 
Metabolic effects 
– Inhibits stress or adrenaline induced glycogenolysis in type 1 DM 
to overcome episodes of hypoglycaemia. 
– Masks the sympathetic manifestation (tremor, tachycardia, 
sweating) of hypoglycemia. 
– Adverse effect on lipid profile : ↓ HDL,↑ LDL & Triglycerides.
CNS effects 
– ↓ decrease in central sympathetic outflow 
– Chronic use leads to sedation, lethargy and disturbances in 
sleep. 
Ocular effects 
– decreases formation of aqueous humour  ↓ intraocular 
pressure
Therapeutic uses 
Cardiovascular use 
– Hypertension 
– Congestive heart failure 
– Angina pectoris : C/I in prinzmetals angina. 
– Cardiac arrythmias. 
– Myocardial infarction: ↓ incidence ,recurrence and mortality 
after long term use
Non cardiovascular use : 
– Migraine prophylaxis 
– Anxiety provoking situations 
– Glaucoma 
– Hyperthyroidism 
– Pheochromocytoma 
– Bleeding oesophageal varices associated with portal 
hypertension
Adverse effects 
– Bronchoconstriction 
– Bradycardia 
– Cold extremities 
– CNS side effects: fatigue ,sleep disturbance and depression 
– Heart failure 
– Hypoglycemia 
– Adverse serum lipid profile
THANK YOU
REGULATION OF TRANSMITTER RELEASE 
• The release of cotransmitters can 
be modulated by prejunctional 
autoreceptors and 
heteroreceptors. 
• Following their release from 
sympathetic terminals, all three 
cotransmitter norepinephrine, 
neuropeptide Y (NPY), and ATP 
can feedback on prejunctional 
receptors to inhibit the release of 
each other. 
• Enhancement of sympathetic 
neurotransmitter release can be 
produced by activation of b2 
adrenergic receptors
DRUGS THAT AFFECT ADRENERGIC NEURONS

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Adrenergic receptors and its modulators

  • 1. ADRENERGIC RECEPTORS AND MODULATORS Dr Imran Zaheer JNMCH, AMU Aligarh
  • 3. Sympathetic System  Preganglionic fibers originate from • Thoracic (T1-T12) segments of the cord • Lumbar (L1-L3) segments of the cord  Most of the ganglia are located in paravertebral chains that lie along the spinal cord  Few (prevertebral) on the anterior aspect of the aorta  Preganglionic fibers are short and the postganglionic fibers are long
  • 4. NEUROTRANSMITTERS • 3 types Collectively called catecholamines 1. Noradrenaline(NA)at postganglionic sympathetic sites(except sweat glands, hair follicles) & in certain areas of brain. 2. Adrenaline(Adr)secreted by adrenal medulla 3. Dopamine(DA)transmitter in basal ganglia, limbic system, CTZ, anterior pituitary.
  • 5. occurs in adrenergic neuronal cytoplasm occurs inside granules occurs in adrenal medulla
  • 6. STORAGE OF TRANSMITTER • Stored in synaptic vesicles or granules within adrenergic nerve terminal. • Vesicular membrane actively takes DA from cytoplasm & synthesize NA inside vesicle with help of DA β-hydroxylase. • NA stored in a complex with ATP(4:1) adsorbed on protein chromogranin A. • In adrenal medulla, NA thus formed is diffuses into cytoplasm where it is methylated to Adr. • Adr so formed is stored in separate granule  Chromaffin granule.
  • 7. RELEASE OF TRANSMITTER • Depolarisation of nerve terminal membrane opens calcium channels in nerve terminal membrane & resulting entry of Ca2+ promoting fusion and discharge of synaptic vesicles
  • 8. REGULATION OF TRANSMITTER RELEASE • Release of cotransmitters can be modulated by prejunctional autoreceptors and heteroreceptors. • Following their release from sympathetic terminals, all three cotransmitter norepinephrine, neuropeptide Y (NPY), and ATP can feedback on prejunctional receptors to inhibit the release of each other. • Enhancement of sympathetic neurotransmitter release can be produced by activation of b2 adrenergic receptors
  • 9. UPTAKE OF NEUROTRANSMITTER Transport of noradrenaline Uptake 1 (Norepinephrine Transporter) Uptake 2 (Extraneuronal amine Transporter) Vasicular Transporter (VMAT- 2) Specificity NA > A A > NA NA = A Location Neuronal membrane Non-neuronal cell membrane (smooth muscle, cardiac muscle, endothelium) Synaptic vesicle membrane Other substrates Tyramine guanethidine (+)-Noradrenaline Histamine Dopamine 5-HT Inhibitors Cocaine Tricyclic Antidepressants (e.g. desipramine Steroid hormones (e.g. corticosterone) Phenoxybenzamine Reserpine
  • 10. Metabolism of neurotransmitter • Endogenous & exogenous catecholamines are metabolised mainly by two enzymes, monoamine oxidase & catechol-O-methyl transferase (COMT). • MAO occurs within cells bound to surface membrane of mitochondria, abundant in noradrenergic nerve terminals. • COMT a widespread enzyme that occurs in both neuronal and non-neuronal tissues, acts on both catecholamines & its deaminated products, produced by action of MAO. • Main final metabolite of adrenaline & noradrenaline is 3-methoxy- 4-hydroxymandelic acid (VMA).
  • 11. DEAMINATION DEAMINATION ALDEHYDE DEHYROGENASE ALDEHYDE REDUCTASE 3,4-DIHYDROXYPHENYL GLYCOL 3,4-DIHYDROXYMANDELIC ACID 3-METHYL,4-HYDROXYPHENYLGLYCOL ALCOHOL DEHYROGENASE ALDEHYDE DEHYROGENASE VANILLYL MANDELIC ACID
  • 12. ADRENERGIC RECEPTORS • All belong to superfamily of G-protein-coupled receptors
  • 13. α1 α2 β1 β2 β3 Second messengers and effectors PLC activation ↓cAMP ↑cAMP ↑cAMP ↑cAMP ↑ IP3 ↑DAG ↑Ca2+ Selective agonists Phenylephrine, methoxamine Clonidine, clenbuterol Dobutamine, xamoterol Salbutamol, terbutaline, salmeterol, formoterol BRL 37344 Selective antagonists Prazosin, doxazocin Yohimbine, idazoxan Atenolol, metoprolol Butoxamine
  • 14. Effects of receptor activation Tissues and effects α1 α2 β1 β2 β3 Blood vessels Constrict Constrict Dilate Bronchi Constrict Dilate GI tract Relax Relax (presynaptic effect) Relax GI sphincters Contract Uterus Contract Relax Bladder Relax detrusor
  • 15. α1 α2 Β1 Β2 β3 Bladder sphincter Contract Seminal tract Contract Relax Iris (radial muscle) Contract Ciliary muscle Relax Heart: Rate Increase Force of Increase contraction
  • 16. α1 α2 β1 β2 β3 Liver Glycogenolysis Glycogenolysis Fat Lipolysis Thermogenesis Pancreatic islets Decrease insulin secretion
  • 17. α1 α2 β1 β2 β3 Nerve Terminal: Adrenergic Decrease release Increase release Cholinergic Decrease release Salivary gland K+ release and watery secretion Amylase secretion Mast cells Inhibition of histamine release
  • 18. Receptor Regulation • Responses mediated by adrenoceptors are not constantly same. • Three processes have considerable clinical significances. 1. Desensitisation 2. Up – Down regulation 3. supersensitivity
  • 19. DRUGS THAT AFFECT ADRENERGIC RECEPTOR
  • 20. DRUGS THAT AFFECT ADRENERGIC NEURONS
  • 21.
  • 22. Therapeutic Classification of Adrenergic Drugs • Pressure agents Noradrenaline Ephedrin Dopamine Phenylephrine Methoxamine • Cardiac stimulants Adrenalin Dobutamine Isoprenaline • Bronchodilators Isoprenal Salbutamol Salmeterol Formoterol • Nasal Decongestants Phenylephrine Xylometazoline Oxymetazoline Naphazoline • CNS Stimulants Amphetamine Methamphetamine Dexamphetamine • Anorectics Fenfluramine Sibutramine Dexfluramine • Uterine relanxant & vasodilators Ritodrine Isoxsuprine Salbutamol Terbutaline
  • 23. Clinical uses of adrenoceptor agonists • Cardiovascular system – cardiac arrest: adrenaline – cardiogenic shock: dobutamine (β1-agonist) – heart block: β-agonists (e.g. isoprenaline) can be used temporarily while electrical pacing is being arrange • Anaphylactic shock (acute hypersensitivity) – adrenaline is the first-line treatment along with steroids & antihistaminics • Respiratory system – Asthma : selective β2-receptor agonists (salbutamol, terbutaline, salmeterol, formoterol) – nasal decongestion: drops containing oxymetazoline or ephedrine for short-term use
  • 24. • Miscellaneous indications – adrenaline can be used to prolong local anaesthetic action – miscellaneous indication for α2-agonists (e.g. clonidine) include hypertension , menopausal flushing, lowering intraocular pressure & migraine prophylaxis – Obesity – CNS uses • Hyperkinetic children • Narcolepsy
  • 25. TOXICITY OF ADRENERGIC DRUGS • Restlessness, palpitation, anxiety, tremor, may occur after s.c. /i.m. injection of Adr. • Marked rise in BP leading to cerebral haemorrhage. • Ventricular tachycardia/fibrillation, angina, myocardial infarction are the hazards of large doses of Adr. • CNS toxicity is rarely observed with adr. drugs – In moderate doses, amphetamines commonly cause restlessness, tremor, insomnia, & anxiety; in high doses, a paranoid state may be induced.
  • 26. ADRENERGIC ANTAGONISTS • These are drugs which antagonize the receptor action of adrenaline and related drugs. • They are competitive antagonists at α or β or both α and β. 1. α ADRENERGIC BLOCKING DRUGS 2. β ADRENERGIC BLOCKING DRUGS
  • 27. α ADRENERGIC BLOCKING DRUGS I. Nonequilibrium type  B-Haloalkylamines - Phenoxybenzamine. ll. Equilibrium type A. Nonselective (i) Ergot alkaloids-Ergotamine, Ergotoxine (ii) Hydrogenated ergot alkalolds-Dihydroergotamine(DHE), Dihydroergotoxine (iii) Imidazolines-- Phentolamine (iv) Miscellaneous - Chlorpromazine B. α1 selective- Prazosin, Terazosin, Doxazosin, Tamsulosin C. α2 selective- Yohimbine
  • 28. Pharmacological properties  Cardiovascular effect • Blockade of α receptors → vasodilatation → decrease in peripheral vascular resistance → fall in BP → Hypotension. • Resultant fall in BP → baroreceptor reflex → sympathetic discharge since α receptors are blocked, stimulates β1 receptor in heart → tachycardia • α receptors blocked → absence of efficient peripheral vasoconstriction in erect posture → peripheral pooling of blood → cerebral hypoxia , vertigo and fainting → postural hypotension
  • 29. • Nasal stuffiness due to blocked of α receptor in nasal blood vessels. • Miosis due to loss of tone of radial muscles of iris. • Tone of smooth muscle in bladder trigone, sphincter and prostate is reduced by blockade of α1 receptor → urine flow in patients with benign hypertrophy of prostate (BHP) is improved. • Inhibition of contractions of vas deferens and ejaculatory duct → failure of ejaculation → impotence • Intestinal motility is increased due to partial inhibition of relaxant sympathetic influences → diarrhoea
  • 30. β ADRENERGIC BLOCKING DRUGS Nonselective (β1 and β2 ) a. Without intrinsic sympathomimetic activity Propranolol, Sotalol, Timolol. b. With intrinsic sympathomimetic activity Pindolol c. With additional α blocking property Labetalol, Carvedilol Cardioselective (β1) Metoprolol, Atenolol, Acebutolol, Bisoprolol Esmolol, Betaxolol, Celiprolol, Nebivolol
  • 31. Classifying B blockers into 3 generations
  • 32. Pharmacological properties Cardiovascular system • ↓ heart rate, ↓ myocardial contractility, ↓ conduction velocity,↓ myocardial oxygen demand Though β1 receptor blockade is the main mechanism responsible for antihypertensive effect : - ↓ renin release - ↓ decrease in central sympathetic outflow - Chronic ↓ in c.o - Blockade of facilitatory effect of presynaptic β2 receptor on NE release.
  • 33. Pulmonary system – Least affect on bronchial muscle of normal individuals. – In asthmatic or COPD pts→ severe bronchoconstriction. Metabolic effects – Inhibits stress or adrenaline induced glycogenolysis in type 1 DM to overcome episodes of hypoglycaemia. – Masks the sympathetic manifestation (tremor, tachycardia, sweating) of hypoglycemia. – Adverse effect on lipid profile : ↓ HDL,↑ LDL & Triglycerides.
  • 34. CNS effects – ↓ decrease in central sympathetic outflow – Chronic use leads to sedation, lethargy and disturbances in sleep. Ocular effects – decreases formation of aqueous humour  ↓ intraocular pressure
  • 35. Therapeutic uses Cardiovascular use – Hypertension – Congestive heart failure – Angina pectoris : C/I in prinzmetals angina. – Cardiac arrythmias. – Myocardial infarction: ↓ incidence ,recurrence and mortality after long term use
  • 36. Non cardiovascular use : – Migraine prophylaxis – Anxiety provoking situations – Glaucoma – Hyperthyroidism – Pheochromocytoma – Bleeding oesophageal varices associated with portal hypertension
  • 37. Adverse effects – Bronchoconstriction – Bradycardia – Cold extremities – CNS side effects: fatigue ,sleep disturbance and depression – Heart failure – Hypoglycemia – Adverse serum lipid profile
  • 39. REGULATION OF TRANSMITTER RELEASE • The release of cotransmitters can be modulated by prejunctional autoreceptors and heteroreceptors. • Following their release from sympathetic terminals, all three cotransmitter norepinephrine, neuropeptide Y (NPY), and ATP can feedback on prejunctional receptors to inhibit the release of each other. • Enhancement of sympathetic neurotransmitter release can be produced by activation of b2 adrenergic receptors
  • 40. DRUGS THAT AFFECT ADRENERGIC NEURONS