It deals with the basics of autonomic nervous system and cholinergic drugs / cholinomimetics / parasympathomimetic drugs

1. Autonomic nervous system and
cholinomimetics
By Dr Kumar Gourav
PG resident, pharmacology

2. Nervous system

3. Peripheral nervous system
 The peripheral nervous system (PNS) is
the division of the nervous system
containing all the nerves that lie outside of
the central nervous system (CNS).

4. Peripheral nervous system
 Somatic nervous systen
the part of the peripheral nervous system
responsible for carrying sensory and motor
information to and from the central nervous
system.
 Autonomic nervous system
is the part of the peripheral nervous system
responsible for regulating involuntary body
functions, such as blood flow, heartbeat,

6. Autonomic nervous system
 It is further divided into two branches:
1. sympathetic system regulates the flight
or fight responses
2. parasympathetic system helps maintain
normal body functions and conserves
physical resources.

10. Cholinergic system
 Neurotransmitters – acetylcholine
Acetylcholine:
It is hydrolysed by enzyme cholinesterases.
cholinesterases
true cholinesterases pseudocholinesterases

12. Cholinergic receptors
• Present in heart, smooth
muscle, exocrine glands
and CNS
Muscarinic
(M)
• Located in neuromuscular
junction(NMJ), autonomic
ganglia and adrenal medulla
Nicotinic
(N)

13. Classification

14. Muscarinic actions
1. Cardiovascular system
a. Heart : bradycardia
conduction is slowed
force of contraction reduced
b. Blood vessels: vasodilation
decreased BP

15. Muscarinic actions
2. Smooth muscle:
a. Gastrointestinal tract:
increases tone of the gut
peristaltic movements
increases GI secretion
relaxes the sphincter(defecation)

16. Muscarinic actions
b. Urinary bladder:
contracts detrusor muscle
relaxes the trigonal sphincter
(urination)

17. Muscarinic actions
c. Bronchi :
Contracts bronchial smooth muscle
(Bronchospasm)
Inc tracheobronchial secretion
Hence contraindicated in bronchial asthma

18. Muscarinic actions
3. Exocrine glands:
increases all secretion like salivary,
lacrimation, sweat, bronchial, gastric etc.
4. Eye :
does not produce any effect on topical
application because of its poor
penetration through tissues.

19. Nicotinic actions
 To elicit nicotinic actions, larger doses of Ach is
required
1. Autonomic ganglia:
tachycardia, hypertension
2. Skeletal muscle:
twitching, fasciculation, paralysis
3. CNS:
No effect. (does not cross BBB)

20. USES
 Pilocarpine is used only in the eye as 0.5–
4% drops.
 It is a third-line drug in open angle
glaucoma.
 It facilitates drainage of aqueous humour
and reduces the intraocular pressure (IOP)

21. Anticholinesterases
 Anticholinesterases (anti-ChEs) are agents
which inhibit Cholinesterases and protect
ACh from hydrolysis.
 Hence Ach gets accumulates in muscarinic
and nicotinic sites producing cholinergic
effects.
 Hence it is called indirectly acting
cholinergic drugs

23. uses
1. As miotic in glaucoma
2. Myasthenia gravis
3. Postoperative paralytic ileus / urinary
retention
4. Curare poisoning
5. Belladona poisoning
6. Alzheimer’s disease

24. Myasthenia gravis
 An autoimmune disorder
 Development of antibodies against nicotinic
receptors (NR) at the muscle endplate
 Weakness and easy fatigability on repeated
activity
 Recovery after rest.

25. Treatment
 Neostigmine/pyridostigmine – allow ACh
released from prejunctional endings to
accumulate and act on the receptors .
 Corticosteroids afford considerable
improvement by their immunosuppressant
action.

26. Treatment
 Other immunosuppressants like
azathioprine and cyclosporine
 Edrophonium aggravates MG

27. OP poisoning
 Signs and symptoms
1. Muscarinic effects: Irritation of eye,
lacrimation, salivation, sweating, copious
tracheo-bronchial secretions, miosis,
blurring of vision, bronchospasm,
breathlessness, colic, involuntary
defecation and urination.

28. OP poisoning
2. Nicotinic effects: Muscular fasciculations,
weakness, respiratory paralysis (central as
well as peripheral).
3. Central effects: Irritability, disorientation,
unsteadiness, tremor, ataxia, convulsions,
coma and death.
• Death is generally due to respiratory failure.

29. Treatment
1. Termination of further exposure to the
poison— fresh air, wash the skin and
mucous membranes with soap and
water,
2. gastric lavage according to need.
3. Maintain patent airway,
4. positive pressure respiration if it is

30. OP poisoning treatment
5.Supportive measures — maintain BP,
hydration, control of convulsions with
judicious use of diazepam.
6. Specific antidotes—
(a) Atropine
(b) Cholinesterase reactivators like
pralidoxime