Cholinergic Transmission And Its Presynaptic Modification Flashcards
What is the rate limiting step of Ach synthesis?
Choline/Na+ costransporter
What inhibits the Choline/Na+ cotransporter?
Hemicholinium
What does Botulinum toxin do?
BT inhibits the fusion of the NT vesicle to the pre-synpatic membrane via cleavage of Synaptobrevin
What is the effect of Hemichonlinium?
Indirect acting
decreases ACh production
Decreased Nicotinic and Muscarinic stimulation
What are the clinical indications of Botulinum toxin?
Blephamospasm dystonias strabismus hemifacial spasm Cosmetic use Hyperhydrosis
What is the onset of action of Botulinum toxin?
2-3 days
What is the duration of action of Botulinum toxin?
3 months
Where is the Nn type nicotinic receptor found?
CNS
Adrenal Medulla
Autonomic Ganglia
Where is the Nm nicotinic receptor found?
NMJ
What inhibits ganglionic receptors?
Mecamylamine
What inhibits NMJ?
Atracurium
What are the mechanisms of cholingergic presynaptic stimulation?
- 4-aminopyridine
- alpha - iatrotoxin
- Higher EC calcium level
- Inhibition of presynaptic inhibitory receptors
What are the mechanisms of cholinergic presynaptic inhibition at the level of synthesis?
Hemicholinium
What are the mechanisms of cholinergic presynaptic inhibition at the level of storage?
Vesamicol
What are the mechanisms of cholinergic presynaptic inhibition at the level of release?
Botulinum toxin, w-conotoxin
What are the mechanisms of cholinergic presynaptic inhibition at the level of choline re-uptake?
Hemicholinium
What are the mechanisms of cholinergic presynaptic inhibition at the level of the NMJ?
Aminoglycosides
Tetracyclins
What are the tertiary ganglion blocking agents?
Mecamylamine
Trimetaphan
What are the quaternary ganglion blocking agents?
Hexamethonium
Tetraethylammonium
What are the non competitive (depolarising) ganglion blocking agents?
Nicotine
What are the competitive (non-depolarising) ganglion blocking agents?
Mecamylamine
Trimetaphan
Hexamethonium
Tetraethylammonium
What receptor do ganglionic blocking agents act on?
Nn receptors (Nn blockers)
What are the characteristics of ganglionic blocking agents?
Non-selective
Unpredictable response thus rarely used in clinical practice
reduce the autonomic tone
prevent baroreceptor reflex changes in heart rate