# The role of salivary sodium in gustatory responses to salt and water in humans

> **NIH NIH R01** · JOHN B. PIERCE LABORATORY, INC. · 2020 · $378,576

## Abstract

PROJECT SUMMARY
 How the vital nutrients of salt and water are sensed is not fully understood. This project will investigate these
two questions in humans based upon preliminary data that suggest sodium (Na+) in saliva is an important factor
in the mechanisms for sensing both nutrients. This possibility first came to light via a chance finding that exposing
the tongue tip to water prior to tasting NaCl interfered with perception of saltiness and increased perception of
NaCl's sweet and sour side-tastes. A subsequent experiment indicated that these effects could be counteracted
by adding NaCl to water in concentrations similar to Na+ in saliva. These results provide the first evidence that
salivary Na+ may be important for encoding the quality of salt taste in humans and raises the possibility that rapid
dilution and rinsing of salivary Na+ from the mouth serves as a gustatory signal for water. A preliminary fMRI
study has supported this hypothesis by showing that adding salivary concentrations of Na+ in the form of NaCl
markedly reduces the normal brain response to water, particularly in gustatory cortex. Together these data
suggest that Na+ in saliva provides a steady-state gustatory signal from which positive deviations are consistent
with the arrival of salt, and negative deviations signal the arrival of pure water. We will build upon the preliminary
data to test this overarching hypothesis via 3 specific aims: Aim 1 will determine if salivary Na+ facilitates
encoding of NaCl saltiness rather than its side-sides tastes by measuring the taste quality and intensity of
suprathreshold NaCl after exposure to pure water compared to after exposure to water containing NaCl and/or
NaHCO3. KCl and KHCO3 will also be tested to rule-out osmolarity as a factor, and Na+ in unstimulated saliva
will be measured (here and in Aims 2 & 3) to determine if salivary Na+ contributes to individual differences in
perception of the NaCl side-tastes. Aim 2 will investigate the peripheral mechanisms and perceptual properties
of the sweet and sour side-tastes using lactisole to block activity in the sweet taste receptor TAS1R2/TAS1R3
and amiloride to block the sodium channel ENaC. Finally, Aim 3 will use fMRI to test the hypothesis that the
gustatory brain response to pure water depends on rinsing salivary Na+ from the tongue by measuring the
response to water with and without a wide range of NaCl concentrations that encompass salivary levels of Na+.
KCl will again be tested to rule-out osmolarity as a factor, and amiloride will also be used to block ENaC to
determine if the gustatory brain response to water depends upon Na+ signaling via this channel.

## Key facts

- **NIH application ID:** 9936375
- **Project number:** 5R01DC017159-02
- **Recipient organization:** JOHN B. PIERCE LABORATORY, INC.
- **Principal Investigator:** BARRY G GREEN
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $378,576
- **Award type:** 5
- **Project period:** 2019-06-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9936375

## Citation

> US National Institutes of Health, RePORTER application 9936375, The role of salivary sodium in gustatory responses to salt and water in humans (5R01DC017159-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9936375. Licensed CC0.

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