Synaptic transmission: Postsynapse Flashcards
Nicotinic ACh receptor (6):
type + permeable + binds + subunit + domain + gene
- ionotropic channels
- Only permeable to Na+ and K+
- Binds ACh to open the channel
- Composed of 5 subunits
- Each subunit has 4 transmembrane domains (M1-M4)
- Different gene makes each subunit. You can mix and match these subunits in different ways to get different functional properties of the channel.
Nicotinic ACh receptor
Explain how permeability to both Na+ and K+ dictate the EPSC at different potentials:
Nicotinic ACh receptor
Explain the glass electrode experiment of isolating a single ligand gated channel
Single channel opens —– manner
all or none
Nicotinic ACh receptor
What dictates the shape of EPSC?
Ie. Fast rise and slow decay
- Opening of multiple postsynaptic receptor/channels in response to binding NT occurd quickly and almost simultaneously. Each individual channel causes square like current and it is the summation of all these openings that gives you the shape of the EPSC or EPSP. However, the closure of individual channel varies. Some close quickly, while others stay open in a non linear manner (almost exponential where the 1st few channel close rapid and a much longer lag for those final channel to clsoe).
The AMPA receptor (6)
main + role + subunit + domain + in vivo + permeability
- The main synaptic depolarizing force in brain
- The glutamate postsynapse has numerous AMPA receptors which depolarize the postsynaptic neuron upon binding glutamate
- 4 different subunits: GLUR1-4 and 4 subunit per channel
- In vivo, channels are a heteromeric: combinations of subunit (not all the same) as mixing different GLUR 1-4 make AMPA channel in diff combination
- AMPA receptors are usually Ca2+ impermeable (only pass N= and LK+)
The NMDA receptor (5)
Location + permeable + subunits + functional + combinations/cobble
- Located postsynaptically with AMPA receptors
- They are plasticity gatekeepers of excitatory synapse as they are permeable to Ca2+ in addition to Na+ and K+
- There are 7 different subunits: NR1 (Obligatory subunit), NR2Am NR2B, NR2C, NR2D, NR 3A, NR3B
- Functional channels require two NR1 and a type of NR2 subunits
- Different subunit combinations affect channel kinectics (current size and duration). You can cobble together the receptor to get different functional property such as different open times, permeability to Ca2+, sensitivity, voltage and sensitivity to Mg2+
NMDA subunit function (3)
NR1, NR2, NR3
NR1: Glycine/d-serine binding site (co-agonist) Oblugatory subunit
NR2: Glutamate binding site
NR3: “Attenuating” function. Channels containing NR3A have a smaller unitary conductance, shorter open time and lower Ca2+ permeability. Can change how well Mg2+ bind to it and Ca2+ pass through it
Explain the process of AMPA to NMDA receptors (3):
- Excitatory glutamate transmission where Gluatamate binds to AMP and NMDA
- Small amount of initial depolarization is only able to open AMPA receptor and allow depolarization by allowing Na+ in and K+ out to move closer to AP threshold
- The opening of AMPA allows enough depolarization that Mg2+ blocker pops out. if the glutamate and cofactor are present/released presynaptically, NMDA receptor are opened.
Mg2+ ions like to block channel at —– potention aka at —–
- hypperpolarized
- rest
How is GABA made?
GABA A receptor (5)
type + found where + ion + drugs + subunit
- Main inhibitory ionotropic receptor/channel in the brain
- Found at the postsynaptic appose to GABAergic nerve terminals (the presynaptic terminals from inhibitory neurons)
- Move Cl-
- alot of clinic/street drugs with depressive affect on the CNS attach here Seizure/anxiety drugs
- composed of 5 subunits put together to make a functional channel: 2 alpha, 2 beta, 1 gamma.
GABA A receptor are permeable to Cl- ions, which enter the cell to hyperpolarize the neuron but this depends on Vm and the reversal potential for Cl- which is normally around -60mV, similar to the resting potential of the neuron. If the neuron is depolarized above -60mV Cl- will —–, but if the Neuron is hyperpolarized below -60mV Cl- will —–
- enter
- leave
Early developing GABA synapse use to be excitatory during prenatal to just post natal, explain:
- NKCC1: co transport 2 Cl-, Na+ and K+ into the cell rausung the intracellular concentration of Cl- pushing the Cl- reversal potential to -30mv. At rest, -65mv, below the potential, CL driving force is to leave and thus, Cl- will exit the cell through GABA A receptor when the receptor opens.
- SHortly after birth, inhibitory neuron shows KCC2 and this moves Cl- out of cell lowering the intracellular concentration of Cl- and the membrane revrsal of Cl- is now -65mv closer to the resting potential. When GABA binds to the receptor, there is an inward movement of Cl-, hyperpolarizing the cell.
Axo-dendritic
Axo-somatic
Axo-axonic
- excitatory (glutamateric) for spine and shaft can be excitatory or inhibitory.
- Inhibitory (GABAergic)
The effectiveness of both excitatory and inhibitory synaptic potentials depends on the current membrane potential. When the neuron is hyperpolarized, EPSPs are —– and IPSPs are —–. When the neuron is depolarized, IPSPs are —– and EPSPs are —–.
- larger
- small
- larger
- smaller
