L13 concepts Flashcards
5 steps in Neurotransmission
- NT synthesis
- Vesicular Storage
- Synaptic Release
- Binding to receptor
- Termination of transmission
Requirements for NT synethesis
precursors
transport into the cell
enzymatic action
Thing that can affect NT synethesis
- therapeutic drugs can inhibit enzymes involved
- dietary intake of certain amino acids can influence availability (low tryptophan intake can reduce serotonin)
- Precursor loading- can increase neurotransmission (L-DOPA in parkinson’s disease)
which NT’s are stored in vesicles?
All except gases and some nucleosides
What are the benefits to storing NTs in vesicles
protects them from degradation by cytosolic enzymes and concentrates them for release (if storage transporters are inhibited then NTs get degraded)
Synaptic Release
Depolarization of the nerve terminal > Ca channels open and Ca influx > SNARE proteins on the vessel interact with SNARE proteins on the membrane > rapid release of NTs
Boxulinum toxin
degrades SNAREs of the cholinergic neuromuscular junction resulting in skeletal muscle paralysis. Can be used to treat muscle spasms
Endocytosed into cholinergic neurons
Degrades SNARES
Prevents calcium-dependent exocytosis of neurotransmitter
amphetamine synaptic release
has affinity for monoamine re-uptake transporters
leads to transporter phosphorylation -which reverses the direct of NT transport
probably also inhibits vesicular uptake proteins
calcium-independent release of neurotransmitter (no voltage change or Ca influx)
SNARES
Enable calcium-dependent docking of vesicle with pre-synaptic membrane
Enable exocytosis of neurotransmitter
indirect acting drugs
can increase neurotransmission and increase the effects of activating a receptor by stimulating the release of endogenous NT
receptor binding
can bind receptors on pre and post synaptic cell membranes
drugs that bind directly to receptors provide the most selective manipulation of synaptic transmission
drugs acting on pre-synaptic receptors to modulate NT release can contribute to some side effects
3 mechanisms for Termination of NT action
- reuptake (can occur at the pre-synaptic nerve terminal, the post-synaptic cell or the surrounding glial cells depending on the location of the reuptake protein)
- Diffusion (out of the synaptic cleft)
- Metabolic transformation and degradation
Dopamine is made from what precursor and by what enzyme?
Tyrosine via tyrosine hydroxylase
Dopamine is a precursor to what molecules
norepinephrine and epinephrine
how is epinephrine formed
tyrosine > DOPA > dopamine > norepinephrine > epinephrine