Pharmacology of Autonomic Nervous System

1. AUTONOMIC NERVOUS
SYSTEM
Saddam Ansari
Tbilisi State Medical University

2. PHARMACOLOGY OF
ANS

3. Objectives
Sympathomimetic drugs (drugs that act on
adrenergic effector organs )
• Drugs that cause release of norepinephrine from nerve
endings
• Drugs that block adrenergic activity
Drugs that act on cholinergic effector organs
• Parasympathomimetic drugs

4. Continued…
• Drugs that have a parasympathetic potentiating effect –
Anticholinesterase drugs
• Drugs that block cholinergic activity at effector organ –
Antimuscarinic drugs
Drugs that stimulate or block sympathetic and
parasympathetic postganglionic neurons
• Drugs that stimulate autonomic postganglionic neurons
• Ganglionic blocking drugs

5. Sympathomimetic Drugs
Drugs that acts like sympathetic stimulation
Causes same effect
There are many drugs
• E.g. norepinephrine, epinephrine, methoxamine
These drugs differs from one another with respect to
• Degree to which they stimulate different sympathetic
effector organs
• Duration of action

6. Continued…
• Epinephrine and norepinephrine have actions only 1 to 2
minutes
• Whereas the actions of other commonly used
sympathomimetic drugs lasts for approximately 30
minutes to 2 hours

7. Continued…
Important drugs that stimulate specific adrenergic
receptors are
• Phenylephrine – alpha receptors
• Isoproterenol – beta receptors
• Albuterol – only beta2 receptors

8. Drugs That Cause Release of
Norepinephrine
Indirect sympathomimetic action
These drugs include
• Ephedrine
• Tyramine
• Amphetamine
These drugs releases norepinephrine from its
storage vesicles in the sympathetic nerve endings.

9. Drugs That Block Adrenergic Activity
• Synthesis and storage of norepinephrine in the
sympathetic nerve endings can be prevented. Best known
drug is RESERPINE
• Release of norepinephrine from the sympathetic endings
can be blocked by GUANETHIDINE
• Sympathetic alpha receptors can be blocked by
PHENOXYBENZAMINE and PHENTOLAMINE

10. Continued…
• The sympathetic beta receptors can be blocked. Drug that
blocks all beta receptors is PROPRANOLOL and
METAPROLOL blocks only beta1 receptors
• Sympathetic activity can be blocked by drugs that block
transmission of nerve impulses through autonomic
ganglia. E.g. HEXAMETHONIUM

11. Parasympathomimetic Drugs
Also known as Cholinergic Drugs
These drugs are not rapidly destroyed by
cholinesterase
Drugs
• Pilocarpine
• Methacholine
Act directly on muscarinic receptors

12. Continued…
Also act on the effector organs of cholinergic
sympathetic fibers and causes:
• Profuse sweating
• Vascular dilatation

13. Anticholinesterase Drugs
It has parasympathetic potentiating effect
Drugs:
• Neostigmine
• Pyridostigmine
• Ambenonium

14. Antimuscarinic Drugs
Blocks cholinergic activity at effector organs
Drugs:
• Atropine
• Homatropine
• Scopolamine
Doesn’t effect on nicotinic action

15. DRUGS THAT STIMULATE OR
BLOCK SYMPATHETIC AND
PARASYMPATHETIC
POSTGANGLIONIC NEURONS

16. Stimulation of Autonomic Postganglionic
Neurons
• Acetylcholine (injected) can stimulates postganglionic
neurons of both systems
• Causes sympathetic and parasympathetic effect
simultaneously
• Nicotine has also causes same effect

17. Ganglionic Blocking Drugs
Blocks impulse transmission from the
preganglionic neurons to the postganglionic
neurons
Drugs:
• Tetraethyl ammonium ion
• Hexamethonium ion
• Pentolinium
These drug’s effects are difficult to control –not
very useful clinically