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Section 6 - (PT1) Drugs Affecting the Autonomic Nervous System
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Uploaded: 7 years ago
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Category: Pharmacology
Type: Lecture Notes
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ca2, muscle, nerve, neuron
postganglionic, acetylcholine, master, potential
na, nicotinic, system
, acetylcholine
receptor
depolarization, affect, possible
action, autonomic, nervous, ganglionic, receptors
, concentration, potential
parasympathet
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Second level
Third level
Fourth level
Fifth level
Click to edit Master title style
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Second level
Third level
Fourth level
Fifth level
Principles of Pharmacology and Toxicology (BIOL3020)
The Autonomic Nervous System
Review of Neurons
Neurons consist of a cell body, axon and nerve terminal
Nerve terminal releases neurotransmitters that can act at other neurons, muscle or glands.
Ganglion is a collection of neuron cell bodies outside the CNS with innervating nerve terminals
Final Target
Cell body
Axon
Nerve terminal
CNS
Ganglion
Basic Anatomy of the Autonomic Nervous System
Basic Anatomy of the Autonomic Nervous System
How is information relayed
n
q
Preganglionic
Postganglionic
CNS
Which chemicals are involved in the autonomic nervous system
(adren)
PreG
PostG
Na
E
mAcR
GPCR
Adren
GPCR
(adren)
The Nicotinic Acetylcholine Receptors
Na
Action Potential
Na
Target Cell
acetylcholine
Preganglionic neuron
Postganglionic neuron
Muscarinic acetylcholine
receptor
Nicotinic acetylcholine
receptor
Depolarization and possible
Action Potential
Parasympathetic System
Action Potential
Na
Target Cell
acetylcholine
Preganglionic neuron
Postganglionic neuron
Nicotinic acetylcholine
receptor
Depolarization and possible
Action Potential
noradrenaline
Sympathetic System
Agonists that affect ganglionic nicotinic receptors
Drugs (agonists) that affect ganglionic nicotinic receptors
Antagonists (Blockers) of ganglionic nicotinic receptors
Y
Y
Action Potential
Na
acetylcholine
Preganglionic neuron
Postganglionic neuron
Target Cell
Muscarinic acetylcholine
receptor
Nicotinic acetylcholine
receptor
Depolarization and possible
Action Potential
Parasympathetic System
The Muscarinic ACh Receptors
mAcR
GPCR
Action Potential
Na
acetylcholine
Preganglionic neuron
Postganglionic neuron
M2
receptor
Nicotinic acetylcholine
receptor
Depolarization and possible
Action Potential
Parasympathetic System
Heart Cell
M2 mAChRs inhibit the heart in two ways
The first way
The G-protein can activate a K channel directly causing hyperpolarization
This inhibits muscle contraction of the heart
ACh
GP
Extracellular
Intracellular
K
K
K
M2
mAChR
hyperpolarization
3
3
GPs
AC
Stimulatory
GPCR
PK
Ca2
Ca2
cAMP
However, the M2 mAChR reduces Ca2 channel opening by inhibiting adenylate cyclase
This decreases cAMP concentration
Therefore, decreases Ca2 conductance
ACh
GPi
Extracellular
Intracellular
AC
M2
mAChR
Ca2
Ca2
M3 mAChRs stimulates glands and smooth muscle
M
M3 mAChRs cause smooth muscle contraction
GP
PLC
M3
mAChR
IP3
Ca2
Ca2
Ca2
ACh
Contraction
ER or SR
M3 mAChRs activation cause gland secretion
GP
PLC
M3
mAChR
IP3
Ca2
Ca2
Ca2
ACh
ER or SR
This increases the concentration of Ca2
Ca2 is responsible for a variety of cellular processes including secretion from glands
Secretion of saliva is via this mechanism
Salivia
mAChRs agonists
)
B
mAChRs antagonists
I
Drugs and toxins that affect acetylcholine concentration at the presynaptic nerve terminal
Ecothiopate
Drugs and toxins that affect acetylcholine concentration at the presynaptic nerve terminal
Once ACh leaves the neuron it is broken down by an enzyme AChE (acetylcholine esterase)
AChE regulates free ACh by converting it back into choline and acetate
Ecothiopate antiAChE used to treat glaucoma as eye drops
Ecothiopate
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