Amiloride-sensitive sodium currents in fungiform taste cells of rats chronically exposed to nicotine

The effects of cigarette smoking and alcohol drinking on salty taste preferences based on Korean Community Health Survey data

BACKGROUND/OBJECTIVES

Excessive sodium intake, cigarette smoking, and alcohol consumption are risk factors for a wide range of diseases. This study aimed to determine whether smokers and drinkers are more likely to enjoy their food with more salt, and whether the combination of smoking and drinking is associated with salty taste preferences.

SUBJECTS/METHODS

This study analyzed the data of over 16 million Koreans from two four-year Korean Community Health Survey cycles (i.e., 2010 to 2013 and 2014 to 2017). The respondents' preferences for salty foods (i.e., their salt intake levels, whether they added salt or soy sauce to foods served on the table, and whether they dipped fried foods in salt or soy sauce), and the odds ratio (OR) of their preference were examined among smokers and drinkers when adjusted for sex, age, body mass index, educational level, household income, marital status, and cigarette smoking or alcohol consumption status.

RESULTS

Cigarette smoking and alcohol consumption were correlated with the consumption of salty food. Based on the adjusted model, cigarette smokers and alcohol drinkers preferred adding salt or soy sauce or dipping fried foods in soybean more than non-smokers and non-drinkers. In addition, people who smoked and consumed alcohol reported a more significant stacking effect regarding the salty taste preference.

CONCLUSION

This large population-based study found that both cigarette smoking and alcohol consumption were correlated with salty taste preferences, which may cause excessive sodium intake.

Changes of the biophysical properties of voltage-gated Na+ currents during maturation of the sodium-taste cells in rat fungiform papillae

Taste cells are a heterogeneous population of sensory receptors that undergo continuous turnover. Different chemo-sensitive cell lines rely on action potentials to release the neurotransmitter onto nerve endings. The electrical excitability is due to the presence of a tetrodotoxin-sensitive, voltage-gated sodium current (I_Na ) similar to that found in neurons. Since the biophysical properties of neuronal I_Na change during development, we wondered whether the same also occurred in taste cells. Here, we used the patch-clamp recording technique to study I_Na in salt-sensing cells (sodium cells) of rat fungiform papillae. We identified these cells by exploiting the known blocking effect of amiloride on ENaC, the sodium (salt) receptor. Based on the amplitude of I_Na , which is known to increase during development, we subdivided sodium cells into two groups: cells with small sodium current (SSC cells; I_Na  < 1 nA) and cells with large sodium current (LSC cells; I_Na  > 1 nA). We found that: the voltage dependence of activation and inactivation significantly differed between these subsets; a slowly inactivating sodium current was more prominent in LSC cells; membrane capacitance in SSC cells was larger than in LSC cells. mRNA expression analysis of the α-subunits of voltage-gated sodium channels in fungiform taste buds supported the functional data. Lucifer Yellow labelling of recorded cells revealed that our electrophysiological criterion for distinguishing two broad groups of taste cells was in good agreement with morphological observations for cell maturity. Thus, all these findings are consistent with developmental changes in the voltage-dependent properties of sodium-taste cells. KEY POINTS: Taste cells are sensory receptors that undergo continuous turnover while they detect food chemicals and communicate with afferent nerve fibres. The voltage-gated sodium current (I_Na ) is a key ion current for generating action potentials in fully differentiated and chemo-sensitive taste cells, which use electrical signalling to release neurotransmitters. Here we show that, during the maturation of rat taste cells involved in salt detection (sodium cells), the biophysical properties of I_Na , such as voltage dependence of activation and inactivation, change significantly. Our results help reveal how taste cells gain electrical excitability during turnover, a property critical to their operation as chemical detectors that relay sensory information to nerve fibres.

Molecular sensor of nicotine in taste of Drosophila melanogaster

Nicotine is an alkaloid and potent parasympathomimetic stimulant found in the leaves of many plants including Nicotiana tabacum, which functions as an anti-herbivore chemical and an insecticide. Chemoreceptors embedded in the gustatory receptor neurons (GRNs) enable animals to judge the quality of bitter compounds and respond to them. Various taste receptors such as gustatory receptors (GRs), ionotropic receptors (IRs), transient receptor potential channels (TRPs), and pickpocket channels (PPKs) have been shown to have important roles in taste sensation. However, the mechanism underlying nicotine taste sensation has not been resolved in the insect model. Here we identify molecular receptors to detect the taste of nicotine and provide electrophysiological and behavioral evidence that gustatory receptors are required for avoiding nicotine-laced foods. Our results demonstrate that gustatory receptors are reasonable targets to develop new pesticides that maximize the insecticidal effects of nicotine.