Flashcards in 1.9 Synaptic Transmission Pt. 1 Deck (28):
What are the general characteristics of Gap Junctions?
-Channels are large/unselective. Metabolic signals can be passed
Where are gap junctions found?
In cardiac muscles, and some smooth muscle
(Cardiac Ventricular, uterus, bladder)
What type of synapse is a a Gap junction?
What are Stellate cells?
Are neurons with several dendrites radiating from the cell body giving them a star shape.
Where are the vesicle, peptide, and enzymes synthesized in the neuron?
Where are non-peptide neurotransmitters made?
Synthesized in the nerve terminal and transported into the vesicle.
What are the three steps to regulation of synaptic vesicle exocytosis?
ii. Discharge of transmitter by exocytosis
iii. Recycling of membrane
What are the three steps of targeting in the regulation of synaptic vesicle exocytosis?
1) Rab protein binds to GTP
2) Hydrolysis of GTP to GDP and inorganic phosphate could be part of the targeting of the vesicle to docking sites
3) Rab proteins are recycled back into the cytoplasm.
What is SNARES?
soluble N-ethylmaleimide-senstiive factor attachment receptors
What is required for exocytosis of synaptic vesicles?
What do synapsins do during transmitter release?
i. Substrates for cAMP-dependent protein kinase and Ca2+/calmodulin dependent protein kinase
ii. When no-phosphorylated the synapsins bind to vesicles to actin filaments in the cytosol.
iii. When phosphorylated due to Calcium entry, the synapsins release the vesicles allowing them to move into the active zone.
What are the steps of vesicle docking and priming?
i. Vesicle proteins ((synaptobrevin) VAMP)
ii. Interact with membrane proteins (SNAP-25 and syntxin)
iii. Dock vesicle to the presynaptic membrane
What cleaves SNARE proteins?
What does Munc18 bind to?
synaptobrevin, but will bind to syntaxin first if present
What does Tetanus target and cleave?
What does Botulinum toxins A, B, and C cleave?
SNAP-25, VAMP, and syntaxin, respectively
What does Alpha Latrotoxin do?
Spider toxin that generates massive vesicle depletion and transmitter release by binding to neurexin, which is a similar to syntaxin.
What does synaptotagmin do to calcium?
1) When calcium enters the presynaptic terminal it binds with synaptotagmin that is in the vesicle wall.
2) Trigers the fusion with the terminal membrane and release of the neurotransmitter from fast synaptic transmission.
What does NSF (N-ethylmaleimide-senstive fusion protein) do?
A cytoplasmic ATPase, NSF (N-ethylmaleimide-sensitive fusion) protein uses SNAP (soluble NSF attachment protein, not related to SNAP-25) to bind to the SNARE complex and unravel it.
What are the criteria for a neurotransmitter?
a.Synthesized in neuron
b.Present in presynaptic terminal and released in significant amounts to produce a clear effect on the postsynaptic neuron or effector organ.
c.When tested exogenously, it behaves as it does endogenously.
d.There is a specific way that it is removed from the synaptic cleft.
What are mechanisms for cleaning up neurotransmitters from the synaptic cleft?
b. Enzymatic degradation (Exp. acetylcholinesterase)
What are methods of Serotonin reuptake?
1. Serotonin is transported back into the nerve terminal.
2. The transporter uses the Na+ gradient to move the serotonin.
3. The serotonin is degraded by MAO intracellularly into 5-hydroxyindoleacetic acid (5-HIAA)
4. 5-HIAA is the primary urinary metabolite of serotonin and can be used to measure 5-HT metabolism.
What are the transporters for monoamines?
There are two, VMAT1 and VMAT2, for monoamines (dopamine, norepinephrine, etc.)
What are the transporter for GABA?
What is the transporter for Acetylcholine?
What can blocking reuptake cause?
Blocking the uptake can lead to longer-lasting effects of the neurotransmitter
(Exp. Cocaine/NE, Tricyclic antidepressants/SSRI’s block serotonin)
What are methods of manipulating synaptic transmission?
a.Altering precursors for synthesis
b. Increasing release
c. Blocking release
d. Inhibiting synthesis
e. Blocking or inhibiting re-uptake
f. Stimulating or inhibiting enzymes that degrade neurotransmitter
g. Binding to a receptor to either block (antagonist) or mimic (agonist) the action of the neurotransmitter.
h. Keeping receptor channel open.