Postsynaptic Mechanisms Flashcards
Excitatory NT and the ion movements it causes?
Glutamate
Influx of Ca or Na
Inhibitory NT and the ion movements it causes?
GABA
Influx of Cl, efflux of K
What effects do alcohol and tranquilisers have on GABA and glutamate?
Alcohol and tranquilisers increase GABA
Alcohol decreases glutamate
What types of receptors are ionotropic?
Ligand-gated ion channels (direct action)
What types of receptors are metabotropic?
G-protein coupled receptors (indirect action via intracellular second messengers)
5 NT-gated ion channels
- ACH-cation channels
- Glutamate-gated Ca/Na channels
- Serotonin-gated cation channels
- GABA-gated Cl channels
- Glycine-gated Cl channels
What ions cause hyperpolarisation and depolarisation respectively?
Hyper: K efflux and Cl influx
Depolarisation: Na influx
GABAa receptors (type, structure, what binds)
Ionotropic receptors for Cl
Heteropentameric with 5 subunits
Binding sites for barbituates, benzos (allosteric modulators) and alcohol
NO intrinsic activity
What are the 3 classes of ionotropic glutamate receptors and how are they distinguished?
Distinguished pharmacologically
AMPA receptor
NMDA receptor
Kainate receptor
NMDA receptors (binding sites, function)
Binding sites for glutamate, Mg, glycine and others
Channel is blocked by Mg at resting potential and deporarisation removes Mg and causes ion flux. (Ca enters)
What is the mechanism of glutamate excitotoxicity?
Excessive release or decreased reuptake of glutamate increases its amount -> postsynaptic iGluR is stimulated ++ (mainly NMDA) and too much Ca enters, causing oxidative and metabolic stress and cell death.
What NT receptors are metabotropic?
Metabotropic glutamate (mGluR1-7)
GABAb receptor
Muscarinic ACh
Various dopamine, 5HT and NA receptors
What is the difference between second-messenger-gated ion channels and G-protein gated ion channels?
In G-protein receptors the alpha subunit of the G protein binds to the ion channel directly to open it, whereas in a second messenger system the alpha unit binds to an enzyme that produces the second messenger, which opens the channel and sends a message to the nucleus of the cell.
