Lecture 7: Peripheral Taste Flashcards
Describe the basic organization of taste receptor cells on the tongue.
- taste buds responding to different modalities are distributed across the tongue
- higher sensitivity to some taste modalities on specific parts of the tongue
Are taste receptor cells (TRCs) neurons?
NO – epithelial cells
Describe receptor expression in TRCs.
there are receptors for only one taste modality in a TRC
Olfaction vs. Gustatory Receptors
olfaction: one family of receptors – all are GPCRs that share downstream signalling pathways
gustatory: different receptor types for each modality – some are GPCRs that share downstream signalling pathways
What do taste buds consist of?
consist of many TRCs, with each TCR tuned to a specific taste modality (expresses the receptor for one of the 5 modalities)
Why are there so many bitter receptors?
different members of T2R family detect different bitter compounds
many more bitter compounds than sweet or umami ∴ need more receptors
Can there be more than one T2R bitter receptor in the same cell?
yes
What can the ENaC channel (receptor for low salt) be blocked by?
amiloride
What taste receptor have cats lost?
no T1R2 – cannot taste sweet
they are obligate carnivores, therefore lost the receptor
What taste receptor have pandas lost?
no T1R1 – cannot taste umami
they eat bamboo (sweet), and do not eat wheat, therefore lost the receptor
What taste receptor have hummingbirds lost?
no T1R2 – but can still taste sweet!
- converted their umami receptor to sweet (through evolution)
- umami receptors now detect very low levels of amino acids
What do results from recording from a nerve show?
it is is recording the activity of many neurons
ie. can therefore show responses to all taste modalities
In high salt conditions, why do mutant salt receptors still behave normally?
still repelled by high salt because this is mediated by a distinct receptor
What is chemogenetics?
activating/silencing neurons with chemicals and receptors
ie. DREADDs, RASSL
What is RASSL?
receptor activated solely by synthetic ligand (before DREADDs)
