NESC 2570 Lecture Notes - Retinoid, Tropomyosin Receptor Kinase A, Taste Bud

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26 Nov 2012
March 27th 2012
1:12 PM
Four transduction mechanisms in the mouth
With five taste receptors
o Bitter
o Sour
o Sweet
o Umami (is an amino acid receptor, MSG)
o Salty
Taste bud
Made up of taste receptor cells
o Have very short axons
o Make their synapses with afferent axons right on the tongue
Transduction in taste buds
Each receptor type is found in its own cell
Sour and salty receptors utilize ion channels
Bitter, sweet, and umami receptors utilize 7-transmembrane g-protein coupled receptors
All these receptors have a relatively slow onset and offset of transduction signalling
Use Serotonin as their signalling neurotransmitter
Voltage gated sodium, potassium, and calcium channels are responsible for the changes in
membrane potential
DO NOT make action potentials
Endothelial sodium channels
These are not voltage sensitive channels
They are receptors for salty food
Increased levels of sodium outside the cell cause a sodium influx, which causes a depolarization of
the cell
Sour taste
This taste is caused by acid (hydrogen ions)
Enter the taste cell through a PKD variant TRP channel
o Which is highly proton permeable
The influx of hydrogen ions causes depolarization
*protons are usually responsible for blocking ion channels, but this special TRP
channel allows for the influx of these hydrogen ions*
Sweet taste
The receptor proteins used in this:
o T1R2
o T1R3
o One 7-transmembrane, g-protein coupled receptor
The alpha subunit binds to PLC
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