Neurotransmitters and Receptors Flashcards
What three ways might a NT be removes from the synaptic cleft?
Diffusion, Reuptake, or Degradation
Criteria for NT? (3)
- Present in Postsynaptic Neuron
- Released in response to presynaptic depolarization causing a Ca influx
- Specific receptors present on the post-synaptic cell
Whats an Ionotropic Receptor?
Receptor directly linked to an ion channel
What are the functional domains of an ionotropic receptor?
Extracellular NT binding site and membrane spanning domain that forms the ion channel
If ionotropic receptor forms one structure, what is it often called?
ligand-gated ion channel
What are ligand-gated ion channels made of?
4-5 protein subunits
What are metabotropic receptors?
Receptors that movement of the ion through the channel requires several metabolic steps
What is a G-protein coupled receptor?
A monomeric protein with an extracellular domain that contains a transmitter binding site and an intracellular domain that binds G proteins
Activation of a G-protein coupled receptor will cause what?
Activation via intracellular messengers
Which type of receptor works more quickly?
Ionotropic receptors
What is a Nicotinic acetylcholine receptor?
An ionotropic acetylcholine receptor
How many subunits does nAChR have?
What are they made of?
Five
A long hydrophobic N-terminal domain, 3 hydrophobic segments, a hydrophilic, and a 4th hydrophobic
Where is the ACh binding site on an nAChR?
near two consecutive cysteines (disulfide bond) on the N-terminal domain
Which segment lines the nAChR pore?
TM2 of each of the 5 subunits
What happens to the nAChR receptor when ACh is bound?
Rotation of TM2 segments. These segments have a kink in the middle of their structure that blocks ion flow through the pore.
What allows choline reuptake in neurons?
Sodium coupled choline transport system
Most excitatory neurons in the CNS are what?
What receptor do they use?
Glutamatergic
Ionotropic glutamate receptor
Two subtypes of ionotropic glutamate receptors?
AMPA and NMDA
What are AMPA channels permeable to? What opens them?
Na and K
Glutamate
What are NMDA channels permeable to? What opens them?
Na, K, and Ca
Require glutamate and partial membrane depolarization
What ion blocks NMDA in a resting membrane?
Mg
Why should we give a shit about NMDA receptors?
They cause long term synaptic modifications that may be important in learning and memory.
What is an NMDA and AMPA receptor made of?
Five subunits.
TM2 segments that don’t completely traverse the membrane
How is glutamate of the nervous system recycled?
After synaptic release, uptake by glial cells. Here they are converted to glutamine and returned to the nerve terminal for conversion back to glutamate.
Name the two main inhibitory neurotransmitters.
GABA and Glycine
Name the types of GABA receptors utilized by inhibitory brain neurons.
GABA-A, GABA-B
What is GABA-A?
Ionotropic GABA gated Cl- channel
What is GABA-B?
Metabolotropic K Channel
What are glycine receptors?
Receptors on inhibitory interneurons that act as ionotropic glycine gated Cl- channels.
Name types of G protein receptors
alpha and beta adrenergic, epinephrine, norepinephrine, GABA-B, metab. glutamete rec, serotonin receptor
Describe G protein couple receptor structure.
7 transmembrane segments. transmitter binding sit, g protein binding site
How do G proteins work? (general)
Activated G proteins act through G protein to activate a primary effector molecule to generate 2nd messenger. This can act on target proteins or activate 2ndary effectors.
Name two specific ways that a G protein may activate a channel.
- Direct interaction with the channel after activation
2, Indirect interaction with the channel following G protein activation (ex. G–>Ad.Cyc.–>cAMP)
Give two signalling advantages of metabotropic receptors.
Amplification of signals, long lasting effects
