GABA synapse and epilepsy

Question 1

Describe the sequence of events at the GABA synapse

Answer 1

Na influx - depolarisation
GABA in vesicles - 40-100000 molecules in each vesicle
vesicles primed so form a close association with the membrane
synaptotagmin in calcium channels
calcium ion channel near primed vesicles - can get rapid response to local calcium influx
drive fusion of vesicles and exocytosis
GABA in synapse
some binds to GABA receptors - other molecules don’t but if enough bind many Cl- may enter
chloride channel opens - 35000 move in through each channel every 1.5ms
at glial cell: GABA transporter - GABA – succinate semialdehyde by GABA transaminase, carbon skeleton is recycled
in nerve cell GABA transporter replenishes vesicles

Question 2

use of epilepsy drug

Answer 2

wide use
can be used in combination of other drugs
and with different types of epilepsy
for specific types of epilepsy you can use specific drugs

Question 3

why don’t drugs modulate the glutamate synapse

Answer 3

don’t want to block the receptors because there are many functions

Question 4

action of tiagabine

Answer 4

inhibits GABA entering the GABA-T and so GABA stays in synapse for longer - have more of an effect

Question 5

action of vigabatrin

Answer 5

inhibit GABA transaminase

so increases level of GABA

Question 6

action phenobarbital

Answer 6

bind to GABA receptor

potentiate response - channel is open longer

Question 7

action of diazepam

Answer 7

bind to GABA receptor
potentiate response
increase the frequency of opening