Neuruotoxins Flashcards
(12 cards)
Tetanus
Clostridium Tetani,
Blocks release of inhibitory NT (glycine,GABA) by proteolytic cleavage of releasing enzymes.
Cholinergic vs Inhibitory Synapse
Depolarization of presynaptic terminal causes Ca2+ channels to open, Ca2+ influx causes release of NT into synapse. (Ach or Glycine).
ACh binds nAChRs ligand gated ion channel Na+ enters and depolarises post synaptic cell action potential propagated. ACh recyled. Excitatory.
Glycine/GABA binds post synaptic glycine/GABA(A) receptors. Ligand gated ion channel allows Cl- ions through to enter post synaptic cell, action potential progpagation chance dececreased. Inhibiotory. Glycine recycled, GABA recycled.
What toxin blocks sodium channel?
Tetrodotoxin (puffer fish)
What toxin activates sodium channel?
Brevotoxin, ciguatoxin
What toxin effects calcium channels?
Conotoxins
What toxin blocks K+ channels?
Dendrotoxins
What toxin causes ablation of terminal?
B-bungarotoxin
C. Botulinum vs C. Tetani
Both molecular weight 150kDA.
BoNT 8 serotypes, 1 TeNT.
Mechanism of action similar but on different neurons, SNARE proetein cleavage.
Flaccid paralysis vs spastic paralysis
Inhibitory vs excitatory
Both cleave synaptobrevin
C. Botulinum general
Prevents release by proteolytic cleavage of presynaptic machinery at autonomic and neuromuscular nerve junctions.
Synaptobrevin -B,E,F,G
SNAP-25- ACE
Synataxin - C
LD50- 0.2ng/kg
Endocytosis of BoNT
Heavy chain portion binds GTIB and synaptotogamin , Locally works
Endocytosis of Tetanus Toxin
Binds gangliosides and peripheral nerve endings internalised and transported retroaxonaly to spinal cord.
Released from motorneuones and taken up by GABAenergic interneurones
Postsynaptic toxins
D-tubocurarine = nAChR antagonist
a-bungarotixns same
Picotoxins blocks GABAa
