Drugs Regulating Neuronal Excitability Flashcards
Benzodiazepines
Allostesic modulator in epilepsy treatment:
Increase GABA receptor activity on motor nerve (inhibitory)
Phenytoin
Epilepsy treatment:
Inhibit Na channel activity (excitatory glutamate input to motor nerve)
Ethosuximide
Epilepsy treatment:
Inhibit T-type Ca channel (excitatory input)
Felbemate
New drug for epilepsy treatment:
?Inhibit NMDA receptor (excitatory glutamate input to motor nerve)
Local anaesthetics
Regional inhibition of pain/sensory pathway in PNS
Can affect other nerves in region (e.g. Motor, autonomic) and excitable tissue
No loss of consciousness
Analgesics
Targets pain/sensory pathway in PNS and CNS
Sets the threshold of pain perception
General anaesthetics
Depresses cortical processing of pain/sensory signals in CNS
Not regionalised
Loss of consciousness
Procaine
Aminoester (local anaesthetic)
Short acting weak base
Hydrolysed by esterases
Lignocaine, bupivacaine, ropivicaine
Aminoamides (local anaestheric)
Longer acting weak base
Undergoes hepatic metabolism
Benzocaine
Different structure to aminoesters and aminoamides
Properties of local anaesthetics
Weak bases differing in onset, duration and toxicity
Reversibly block AP conduction (bind to intraneuronal TM domain of Na channel)
Stabilise axon membrane (no change in resting membrane potential or damage)
Terodotoxin (puffer fish)
Saxitoxin (dinoflagellates)
Lethal toxins
Selective binding to Na channel (similar to local anaesthetics) but on extraneuronal domains
Unsafe in small amounts
Sensitivity of fibres to local anaesthetics
By size: Small > Large
Sensory > Autonomic > Motor
Effect of local anaesthetic is more pronounced in basic or acidic medium?
Greater effect in basic medium because uncharged species is more active (both are essential though)
