pharmacology of parasymphathtic

1. Dr. Haji Bahadar,
Assistant Professor, IPMS-KMU
Drugs acting on parasympathetic
system

2. Introduction
The nervous system is divided into two divisions:
the central nervous system (CNS), which is
composed of the brain and spinal cord, and the
peripheral nervous system, which includes
neurons located outside the brain and spinal cord.
The peripheral nervous system is subdivided into
the efferent and afferent divisions. The efferent
neurons carry signals away from the brain and
spinal cord to the peripheral tissues, and the
afferent neurons bring information from the
periphery to the CNS.

4. Introduction
The autonomic nervous system (ANS), along with the
endocrine system regulate the body functions.
Endocrine system sends signals to target tissues by
varying the levels of blood-borne hormones. In
contrast, the nervous system exerts its influence by the
rapid transmission of electrical impulses over nerve
fibers that terminate at effector cells, which specifically
respond to the release Drugs that produce their
primary therapeutic effect by mimicking or altering
the functions of the ANS are called autonomic drugs.

5. Anatomy of the ANS
 Efferent neurons: The ANS carries nerve
impulses from the CNS to the effector
organs(target organs) by two types of efferent
neurons: the preganglionic neurons and the
postganglionic neurons

6. Parasympathetic neurons
The parasympathetic preganglionic fibers arise
from cranial nerves III (oculomotor), VII (facial), IX
(glossopharyngeal), and X (vagus), as well as from
the sacral region (S2 to S4) of the spinal cord and
synapse in ganglia near or on the effector organs.

8. Neurotransmitters
The autonomic nerve fibers can be divided into two groups
based on the type of neurotransmitter released. If
transmission is mediated by acetylcholine, the neuron is
termed cholinergic. An adrenergic nerve fiber/fibre?? is
a neuron for which the neurotransmitter is either
adrenaline (epinephrine), noradrenaline or dopamine.
 Muscarinic receptors: Muscarinic receptors belong to the
class of G protein–coupled receptors. These receptors, in
addition to binding ACh, also recognize muscarine, an
alkaloid that is present in certain poisonous mushrooms.
M1 receptors are found on gastric parietal cells, M2
receptors on cardiac cells and smooth muscle, and M3
receptors on the bladder, exocrine glands, and smooth
muscle.

10. G protein–coupled receptors
G-protein – protein bound to GTP(Guanosine
triphosphate)
G-protein-coupled receptor (GPCRs) – receptors bound
to G proteins
-G-protein is a switch turned “on” and “off” by the receptor
G-protein then activates an effector protein (usually an
enzyme). Once activated, the effector protein produces a second
messenger. second messenger generates the cellular response to
the original signal For example – one common effector protein is
adenylyl cyclase which produces cAMP as a second messenger.
Other second messengers: inositol phosphates, calcium
ions (Ca2+).

13. (Acetylcholine)

14. Organ system effects of acytlcholine
1. Cardiovascular system:
Effect on heart: Decrease heart rate and cardiac
output(negative chronotropy)
Effect on blood pressure: Decrease in blood
pressure
2. Gastrointestinal system: acetylcholine increases
salivary secretion and stimulates intestinal
secretions and motility.
3. Respiratory System: Enhances bronchiolar
secretions, and bronchoconstriction.
4. Effect on bladder: increase urination
 5. Eye: Miosis (marked constriction of the pupil)

15. Self study
Pilocarpine: Applied topically to the eye,
pilocarpine produces rapid miosis and contraction
of the ciliary muscle.

16. Pilocarpine
 Pilocarpine is used to treat dry mouth caused by
radiotherapy in people with head and neck cancer
and to treat dry mouth in people with Sjogren's
syndrome (a condition that affects the immune
system and causes dryness of certain parts of the
body such as the eyes and mouth).