GABA Flashcards
What is GABA?
Main inhibitory transmitter
What is GABA synthesised from?
Glucose
Describe the synthesis and recycling
1) In mito, glucose -> alpha-ketoglutarate (in Kreb’s cycle)
2) alpha-ketoglutarate -> glutamate (by GABA-transaminase)
3) Glutamate -> GABA (by glutamic acid decarboxylase)
4) Packed into vesicles (via vesicular transporter (VGAT)) and released into synaptic cleft
5) 2 fates:
Uptake into nerve terminal via GAT and packaged back into vesicles
OR
Uptake into star-shaped glial cell (astrocyte) via GAT and mito
GABA -> succinate semialdehyde (which then enter Kreb’s cycle)
What type of neurones is GABA principally present in?
Local interneurons
Name the 3 types of GABA receptors
GABA A
GABA B
GABA C
How does GABA A effect ions?
Opens for Cl- inflow
Causes hyperpolarisation
How many subunits do GABA A receptors have?
5
each has 4 transmembrane segments
How many isoforms do the GABA A subunits have?
alpha = 6 beta = 3 gamma = 3
Name the 5 binding sites of a GABA A receptor
Benzodiazepine Barbiturate/anaesthetic GABA Channel blocking Neurosteroid
Name the 2 drugs that bind to the benzodiazepine binding site of a GABA A receptor
Diazepam
Lorazepam
Name the agonists and antagonists that bind to the GABA binding site of a GABA A receptor
Agonists = GABA, muscimol Antagonists = Bicuculline, gabazine
Name the 2 drugs that bind to the channel blocking site of a GABA A receptor
Picrotoxin
Pentylenetetrazole
Name the 3 drugs that bind to the barbiturate/anaesthetic binding site of a GABA A receptor
Pentobarbital
Thiopental
Propofol
Which type of GABA receptor are typically GPCRs?
GABA B
What effect do GABA B receptors have at the presynaptic terminal?
Closes Ca+ channels
Therefore decreases transmitter release
