Week 12 - Anti-epileptic drugs Flashcards
What are Seizures characterised by? what is their casue?
Excessive asynchronous excitation of a population of cortical neurons
No obvious cause but can be associated an initiating factor like brain tumour, head trauma, drug use, etc
What does a seizure look like in an EEG?
What is epilepsy?
diagnosed if someone has experienced at least two unprovoked seizures occurring more than 24 hours apart
How can you categorise seziures?
Focal onset or Generalised onset
How is a focal onset categorised and what occurs in this?
Aware:
- remains conscious
- altered senses
- generally remembers
Impaired awareness:
- loss of consciousness & recall
How is generalised onset categorised and what occurs in this?
Motor:
- tonic-clonic
- tonic
- myoclonic
- muscle stiffness alternating with spasms
Non-motor:
- absence
What are aims of anti-epileptic drug therapy?
prevent seizures by disrupting neuronal membrane excitability -> block Na+ and Ca2+ channels
What are 3 places to target to enhance GABA neurotransmission?
Target the:
- enzyme GABA transaminase (breaks down GABA in pre-syn neuron)
- GAT-1 transporter
- GABAa receptor
What are GABA transaminase inhibitors and how do they work? eg?
GABA transaminase inhibition -> less breakdown of GABA in pre-synaptic neuron -> increase intracellular releasable stores of GABA
Eg:
Valproate
Vigabatrin
What are GAT inhibitors and how do they work? eg?
GABA is taken up back into (reuptake) the pre-synaptic neuron by GAT
GAT inhibition -> increased extra-neuronal GABA bc less GABA undergoes reuptake
Eg:
Tiagabine
What are GABAa receptor modulators and how do they work? eg?
Endogenous GABA activates GABAa receptor
Benzodiazepines bind allosterically to BDZ receptor site (diff from active site) -> enhances GABA action
Eg:
Benzodiazepines
What is Status Epilepticus?
= continuous seizure activity or repeated seizures w no recovery of consciousness between seizures
duration needs to be at least 30 mins to diagnose
Action potential visualised
What states do Na+ channels exist in?
- Resting
- Open
- Inactivated
What happens to neurons during seizures?
fire at a high freq -> depolarisation shifts equilibrium towards to inactivated state