Lecture 4.1 Flashcards
What are the 3 ways Metabotropic receptors regulate ion channels?
- Coupling of G protein to an ion channel altering permeability
- Coupling of G protein to a 2nd messenger where it directly regulates an ion channel ex/ cAMP/cGMP
- Coupling of G protein to a 2nd messenger leading to ion channel phosphorylation
What are the alpha subunit types of Metabotropic receptors and what do they do?
G(alpha)s- stimulates Adenylyl Cyclase
G(alpha)I- inhibits Adenylyl Clyclase
G(alpha)q- stimulates Phospholipase C
G(alpha)t- inhibits cGMP Phosphodiesterase
G Protein effector pathways (G protein to Adenylate Cyclase)
G Protein- AC-cAMP-PKA (Kinase)
G Protein effector pathways (G protein-PI3 Kinase)
G Protein-PI3 Kinase-Pi3 phosphate-PKB(Kinase)
G Protein effector pathways (G Protein-Phospholipase C)
G Proetin-Phospholipase C- DAG/IP3-PKC and CaCam Kinase respectively
G Protein effector pathways (GProtein-Guanylate Cyclase)
G Protein-Guanylate Cyclase-cGMP-PKG(Kinase)
If signalling is recurrent for a long time what is one thing that could happen?
Gene expression-when cAMP is increased for a longer period, protein kinase A is activated and will go into the nucleus and work with the CREB cycle to increase gene expression
How are receptor signals switched off?
Detachment of ligand
Hydrolysis of GTP back to GDP
Removal of 2nd messengers (could be removed or destroyed)
Activation of phosphorylases
Is switching off receptor signals easier or harder then turning them on?
Switching off is harder and more complicated
How do peptide neurotransmitters get to the axon terminal?
They are synthesised and packaged in the cell body, transported along outside of micro tubules and undergo exocytosis in response to increase in calcium influx. They is also no re-uptake of them
Are peptide neurotransmitters ionotropic of Metabotropic?
Metabotropic
What are some examples of peptide neurotransmitters?
Angiotensin II (thirst and salt appetite) Endorphins Substance P (pain transmission)
Vesicles with peptide transmitters are called?
LDCVs- Large Dense Core Vesicles
What else are inside peptide neurotransmitter vesicles?
Proteins that act as a scaffolding and sometimes peptidases that may act after the release of the neurotransmitter
What do Neuromodulators do?
They alter excitability of the post synaptic neuron but do not regulate the membrane voltage
What are co-transmitters?
They are often peptides, are released from the same synapse as a fast neurotransmitter, co-released
What are auto receptors?
They are present on the pre-synaptic terminal and inhibit release of neurotransmitter
What are non-synaptic receptors?
They are an example of Neuromodulators action, located on the outside of the synapse
In relation to each other, are Metabotropic receptors spread closely or far apart from each other?
More spread out, less dense post synaptic density
Describe the process of desensitisation
When a signal needs to be stopped, a Kinase phosphorylates GRK. This in turn phosphorylates the GPCR. This then binds Arrestin stopping the GPCR
Is it the receptor or the transmitter that determines the nature of neurotransmission?
The receptor!
Transmitters like catecholamines and peptides are ………………transmitters
Metabotropic
What is a property of the Muscarinic ACh receptor that is interesting
It bind to ionotropic (Nicotinic) and Metabotropic receptors (Muscarinic)
What is the effect of Metabotropic stimulation?
Alters ion channel permeability
Slower on set and longer duration then ionotropic
