Introduction to Autonomic Nervous System

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By Dr. Dipesh R. Panday, Department of Clinical Pharmacology &Therapeutics

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Neuron

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Neuron-Neuron Communication

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Nervous System Organization

Muscarinic Nicotinic

M1-3 Nn-Nm528/09/2012

ACTIONS OF SANS AND PANS

SYMPATHETIC SYSTEM PARASYMPATHETIC SYSTEM

3E situations

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Relay-station

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Ganglion: a mass of nerve cellbodies outside CNS

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8

100%

90%

9%

1%

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Which Is More Important?

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Which is more cute?

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Most organs receive dual sympatheticand parasympathetic innervation.

However, some organs only receive sympathetic innervation:SpleenSweat GlandsPiloerector MusclesMost Blood Vessels

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Rest & Digest

Even I have a Paraysmpathetic System28/09/2012

Cholinergic Neuroeffector Junction

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-

Hemicholinium

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Botulinum toxin

CHOLINOMIMETICS

Nicotinic: NicotineMuscarinic: Bethanechol, PilocarpineAChE inhibitors: reversible-edrophoniumAChE inhibitors: irreversible-OP poison

CHOLINORECPTOR BLOCKERSMuscarinic: Atropine, Benztropine, Tropicamide,Glycopyrrolate, ScopolamineNicotinic (NM): Tubocurarine, Atracurium, SuccinylcholineNicotinic (NN): Hexamethonium, Mecamylamine

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Contraction, Secretion15

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These are Ach Esterase inhibitors

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Fight or Flight

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α1 action• Eye-radial (dilator) muscle• Decongestant • Arterioles-contraction(increases BP)• Bladder trigone and sphincter-contraction(anti-diuretic)• Glycogenolysis

• Drugs with selective α1 action: – Oxymethazoline– Phenylephrine– Methoxamine– Dopamine at therapeutic dose.

• α1 selective blocker: Prazosin, Doxazosin, Terazosin, Amsulosin• α nonselective blocker::

Phentolamine(nonselective,irreversible),Phenoxybenzamine(nonselective,irreversible)

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α2 action

• Decrease BP by autoregulation

• Drugs with selective α2 action

– Clonidine

– α -Methyldopa

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β Action• β1 Action: Ionotropic, Dromotropic, Chronotropic action on heart

muscle.

• β2 action((mostly not innervated)– Vasodilation– Bronchioles relaxation– Uterus relaxation

• Preparations:• β agonists:Dobutamine (β1 > β2 ), Isoproterenol (β1 = β2 )

• β2 agonists: Salbutamol, Albuterol, Terbutaline, Ritodrine

• Mixed:Norepinephrine (α1, α2 β1,),Epinephrine (α1, α2, β1, β2)

• β1 (cardioselective) antagonists: Acebutolol, Atenolol, Esmolol• NOTE:Use of Epinephrine: Anaphylaxis, Cardiac Arrest

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Cholinergic Receptor Activators

• Direct activators

• Bethanechol (M), Methacholine, Nicotine (N), Pilocarpine(M)

• Indirect activators

– AChE inhibitors: reversible- Edrophonium, Physostigmine, Neostigmine

– AChE inhibitors: irreversible- Organo-phosphate Poison, Malathion, Parathion

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Cholinergic Receptor Antagonists• Muscarinic blockers: Atropine, Benztropine,

Ipratropium, Glycopyrrolate, Scopolamine

• Ganglionic blockers:Hexamethonium, Mecamylamine

• NMJ blockers:

• Depolarizing: Atracurium, Pancuronium, Tubocurarine

• Nondepolarizing: Succinylcholine2728/09/2012

Adrenergic Receptor Activators

• α1 agonists: Phenylephrine, Methoxamine

• α2 agonists : Clonidine, A-methyldopa

• β agonists: Isoproterenol (β1 = β2 ), Dobutamine (β1 > β2 )

• β2 agonists: Salbutamol,Albuterol, Ritodrine, Terbutaline

• Mixed: Norepinephrine (α1, α2, β1,), Epinephrine (α1, α2 β1, β2)

• Indirect-acting: Amphetamine, Cocaine, Ephedrine2828/09/2012

Adrenergic Receptor Antagonists• α1 antagonists: Doxazosin, Prazosin, Terazosin

• α2 antagonists: Yohimbine

• Mixed α antagonists: Phenoxybenzamine, Phentolamine

• β1 (cardioselective) antagonists: Acebutolol, Atenolol, Esmolol, Metoprolol

• β(nonselective): Pindolol, Propranolol, Timolol

• α & β antagonists: Carvedilol, Labetalol2928/09/2012

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