L8 - Amino Acid transporters Flashcards
what determines whether an AP is fired?
whether the summation of EPSPs and IPSPs (temporal and spatial) reaches the threshold for an AP (-55mV)
what effect does glutamate have when acting on ionotropic receptors
excitatory (fast acting)
opening of Na+ / K+ channels (equally permeable)
what effect does glutamate acting on metabotropic receptors havve
slower acting inhibitory effect (increase IPSPs) (presynaptic inhibition and modifying frequency of postsynaptic APs)
what effect does GABA have when acting on
ionotropic
metabotropic
receptors
inhibitory effect on both
what effect does glycine have and what type of receptor does it act on?
inhibitory
ionotropic
where is glutamate synthesised? and why is this important
synthesised in brain from glucose metabolism
or from glutamine in astrocytes
important as glutamate cant cross BBB
what is the name of the vesicular glutamate transporters
VGluT 1-3
how is a concentration gradient maintained for the transport of NT into vesicles?
H+ ATPase actively pumps H+ into vesicles
each NT transporter can then use this [H+] gradient to transport NT into vesicles via antiport
how is Gutamine transported into glial cells?
EAAT (transporter)
using co transport of 2Na / 3H+ into glial cell
or counter-transport of K+
what are the three classes of ionotropic glutamate receptors
NMDA
AMPA
Kainate
what are the NMDA receptor channels permeable to
Na+
K+
Ca2+
what are the AMPA receptor channels permeable to
all permeable to Na+ / K+
some permeable to Ca2+
what are kainate receptor channels permeable to?
Na+
K+
Ca2+
where are kainate receptors mostly found
pre-synaptically - modulate NT release
how many subunits are there for the AMPA receptor (name them) and how do they exist in the receptor
4
GluA1-4
receptor is a tetramer
subunits exist in pairs, so the receptor will be 2x one type and 2x another type (eg 2x GluA1 and 2x GluA2)
how many subunits does the NMDA receptor have (name them) and how do they exist in the receptor (how many of each type)
5
GluN1
GluN2 (A-D)
receptor is a tetramer
subunits exist as 2x GluN1 then 2x any of the GluN2 subunits
how many subunits does the Kainate receptor have (name them) and how do they exist in the receptor (how many of each type)
5
GluK1-5
tetramer
GluK1-3 can form homomeric receptors, or can combine with 2x another subunit (always pairs)
GluK4-5 have to combine with 2x GluK1-3 (2+2) to be functional
where in brain are AMPA and NMDA receptors found
the different subunit types can be found in diifferent brain regions but AMPA and NMDA are generally found at the same functional excitatory synapses
why is GluN1 expressed in all brain regions?
because a fucntional NMDA receptor must have 2x GluN1 subunits
describe the speed of activation and inactivation of AMPA receptors
fast acting (fast depolarisation) fast decay (inactivation)
why is the AMPA receptor fastly inactivating?
due to relatively low affinity for Glutamate
describe the speed of activation and inactivation of NMDA receptors
slower activating
slower inactivating
why is the NMDA slower inactivating than the AMPA
NMDA has a higher affinity for glutamate - glutamate stays bound for longer so the channel may open and close several times before glutamate dissociates