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Cholinergic Receptors

 

  1. Muscarinic (GPCRs) 

RECEPTOR

MOA

SITE

RESPONSE

M1

Activation of PLC; IP3 and DAG →↑Ca2+ and PKC Depolarization and excitation
(
sEPSP) Activation of PLD2, PLA2
 

CNS; Most abundant in cerebral cortex, hippocampus and striatum
Autonomic ganglia

Glands (gastric and salivary)
Enteric nerve

Increased cognitive function (learning and memory)
Increased seizure activity
Decrease in dopamine release and locomotion Increase in depolarization of autonomic
ganglia
Increase in secretions
 

M2

Inhibition of adenylyl cyclase, cAMP Activation of inwardly rectifying K+ channels
Inhibition of voltage-gated Ca2+ channels.
 

CNS, Heart, smooth muscle, autonomic nerve terminals
 

Heart:SA node: slowed spontaneous depolarization; hyperpolarization, HR
AV node: decrease in conduction velocity Atrium:
refractory period, contraction Ventricle: slight contraction
Smooth muscle:
Contraction
Peripheral nerves:Neural inhibition via autoreceptors and heteroreceptor.
Ganglionic transmission
 CNS:Neural inhibition
Tremors; hypothermia; analgesia
 

M3

Activation of PLC;
IP3andDAG Ca2+ and PKC
Depolarization and excitation (
sEPSP) Activation of PLD2, PLA2

CNS, Abundant in Smooth muscle and Glands
 
 

Smooth muscle Contraction (predominant in some, e.g. bladder)
Glands:
Secretion (predominant in salivary gland)
 

M4

Inhibition of adenylyl cyclase, cAMP Activation of inwardly rectifying K+channels
Inhibition of voltage-gated Ca2+ channels Hyperpolarization and inhibition
 

CNS, particularly forebrain
 

Autoreceptor- and heteroreceptor-mediated inhibition of transmitter release in CNS and periphery
Analgesia; cataleptic activity Facilitation of dopamine release
 

M5

Activation of PLC; IP3 and DAG Ca2+ and PKC
Depolarization and excitation (
sEPSP) Activation of PLD2, PLA2

CNS, dopamine neurons in VTA and substantia nigra
 

Mediator of dilation in cerebral arteries and arterioles (?)
Facilitates dopamine release
Augmentation of drug-seeking behavior and reward (e.g., opiates, cocaine)
 

  

  1. Nicotinic (N)

RECEPTOR

MOA

SITE

RESPONSE

NM

Excitatory; end-plate depolarization
 

Skeletal neuromuscular junction (postjunctional)
 

Skeletal muscle contraction

NN

Excitatory; depolarization; firing of postganglion neuron
 

Autonomic ganglia; adrenal medulla
 

Depolarization and secretion of Catecholamines

CNS NICOTINIC

Pre and postsynaptic excitation
 

CNS; pre- and postjunctional
 

Prejunctional control of transmitter release
 






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