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NESC 2570 (6)

March 27th 2012.docx

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NESC 2570
Stefan Kreuger

March 27th 2012 April-05-12 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  Producing IP3  Which opens calcium permeable TRP channels  Causing a depolarization of the cell Chemical signalling mechanisms  Synaptic o The one we're familiar with o Vesicles get released into the synapse in this method  Paracrine o Similar in a way to synaptic signalling mechanisms o But the distance from the release site to the receptor site is greater o Receptors used in the paracrine mechanism are very sensitive, but the distance between
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