The mammalian amiloride-insensitive non-specific salt taste receptor is a vanilloid receptor-1 variant.
The amiloride-insensitive salt taste receptor is the predominant transducer of salt taste in some mammalian species, including humans. The physiological, pharmacological and biochemical properties of the amiloride-insensitive salt taste receptor were investigated by RT-PCR, by the measurement of unilateral apical Na+ fluxes in polarized rat fungiform taste receptor cells and by chorda tympani taste nerve recordings. The chorda tympani responses to NaCl, KCl, NH4Cl and CaCl2 were recorded in Sprague-Dawley rats, and in wild-type and vanilloid receptor-1 (VR-1) knockout mice. The chorda tympani responses to mineral salts were monitored in the presence of vanilloids (resiniferatoxin and capsaicin), VR-1 antagonists (capsazepine and SB-366791), and at elevated temperatures. The results indicate that the amiloride-insensitive salt taste receptor is a constitutively active non-selective cation channel derived from the VR-1 gene. It accounts for all of the amiloride-insensitive chorda tympani taste nerve response to Na+ salts and part of the response to K+, NH4+ and Ca2+ salts. It is activated by vanilloids and temperature (> 38 degrees C), and is inhibited by VR-1 antagonists. In the presence of vanilloids, external pH and ATP lower the temperature threshold of the channel. This allows for increased salt taste sensitivity without an increase in temperature. VR-1 knockout mice demonstrate no functional amiloride-insensitive salt taste receptor and no salt taste sensitivity to vanilloids and temperature. We conclude that the mammalian non-specific salt taste receptor is a VR-1 variant.
Lyall
Vijay
V
Department of Physiology, Virginia Commonwealth University, Richmond, VA 23298-0551, USA. vlyall@hsc.vcu.edu
Heck
Gerard L
GL
Vinnikova
Anna K
AK
Ghosh
Shobha
S
Phan
Tam-Hao T
TH
Alam
Rammy I
RI
Russell
Oneal F
OF
Malik
Shahbaz A
SA
Bigbee
John W
JW
DeSimone
John A
JA
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002412:Cations / Q000378:metabolism; D002814:Chorda Tympani Nerve / Q000502:physiology; D004232:Diuretics / Q000494:pharmacology*; D005260:Female; D006358:Hot Temperature; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D008322:Mammals; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008903:Minerals / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012492:Salts / Q000494:pharmacology*; D050916:TRPV Cation Channels; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology*; D013816:Thermodynamics
D002412:Cations; D004232:Diuretics; D007473:Ion Channels; D008903:Minerals; D012492:Salts; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C493922:Trpv1 protein, rat; D000584:Amiloride