Transcript Ionotropic & Metabotropic Receptors

Ionotropic &
Metabotropic
Receptors
Lesson 12
Membrane Proteins: Ionophores
Ion Channels
 Non-gated
 always open
 Gated
 chemically-gated
 electrically-gated
 mechanically-gated ~

Chemically-Gated Channels
Ligand-Receptor binding
 Ligand
 neurotransmitters
 drugs
 Receptor proteins
 ligand binds to multiple receptors
 receptor subtypes
 specificity ~

Ligand-Receptors Binding
Binding site
 specific point of ligand & receptor
 Affinity
 attraction
 physical & electrical fit
 NT or drug binds to receptor
  or activity of neuron
 excite or inhibit
 Drugs mimic or block NT message ~

Lock & Key Model

NT binds to receptor
 NT = key
 Receptor = lock
Receptor changes shape
 Excitation or Inhibition?
 Determined by nature of receptor
 NOT NT ~

Receptor Subtypes
Specificity
 Same NT
 Binds to many receptor subtypes
 Produce different effects
 EPSP or IPSP
 All NT systems
 Several subtypes each
 Drug side effects ~


ligand binds to receptor
 activation: EPSP or IPSP
NT
Receptor A
~

Same NT can bind to different -R
 different part of NT ~
NT
Receptor A
Receptor B

Same NT can bind to different -R
 different part of NT ~
NT
Receptor A
Receptor B

Same NT can bind to different -R
 different part of NT ~
NT
Receptor A
Receptor B
Ionotropic receptors
Ligand-gated channels
 Ion channels
 NT directly controls channel
 fast action
 transient ~

Metabotropic Receptors
Requires energy
 GTP
 Neuromodulation
 G protein-gated Ion Channels
 Receptor indirectly controls
channel
 relatively fast, but slower than
ionotropic ~

G protein-gated Ion Channels
R
G
GDP
G protein-gated Ion Channels
R
G
GTP
G protein-gated Ion Channels
R
G
GTP
Pore
Metabotropic receptors:
2d messenger systems
2d messenger systems
 Effects relatively slow
 long-lasting
 Signal amplification
 Effects
 Control channel
 Alter properties of receptors
 regulation of gene expression ~

2d Messenger Systems

Signal amplification
 1 NT  activate enzyme 
 ATP 1000s cAMP  10,000s 
 cAMP  10,000s phosphates ~
2d Messenger Systems



External signal
 NT = 1st messenger
Membrane-associated
components
 Receptor
 Transducer
 Primary effector
Intracellular
 2d messenger
 Secondary effector ~
external signal: nt
Receptor
transducer
primary
effector
2d messenger
secondary effector
2d Messenger Systems
Primary Effector
Enzyme
R
G
GTP
*
GDP
Secondary
Effector
2d Messenger Systems
Primary Effector
Enzyme
R
G
GTP
Secondary
Effector
2d Messenger Systems
Primary Effector
Enzyme
R
G
ATP
GTP
cAMP
Secondary
Effector
2d Messenger Systems
Primary Effector
Enzyme
R
G
ATP
GTP
cAMP
Secondary
Effector
P
2d Messenger Systems
Primary Effector
Enzyme
R
G
ATP
GTP
P
cAMP
Secondary
Effector
Pore