sb-366791 and benzamil

Transient receptor potential (TRP) subfamily M member 5 (TRPM5) cation channel is involved in sensing sweet, bitter, umami, and fat taste stimuli, complex-tasting divalent salts, and temperature-induced changes in sweet taste. To investigate if the amiloride- and benzamil (Bz)-insensitive NaCl chorda tympani (CT) taste nerve response is also regulated in part by TRPM5, CT responses to 100 mM NaCl + 5 μM Bz (NaCl + Bz) were monitored in Sprague-Dawley rats, wild-type (WT) mice, and TRP vanilloid subfamily member 1 (TRPV1) and TRPM5 knockout (KO) mice in the presence of resiniferatoxin (RTX), a TRPV1 agonist. In rats, NaCl + Bz + RTX CT responses were also monitored in the presence of triphenylphosphine oxide, a specific TRPM5 blocker, and capsazepine and N-(3-methoxyphenyl)-4-chlorocinnamid (SB-366791), specific TRPV1 blockers. In rats and WT mice, RTX produced biphasic effects on the NaCl + Bz CT response, enhancing the response at 0.5-1 μM and inhibiting it at >1 μM. The NaCl + Bz + SB-366791 CT response in rats and WT mice and the NaCl + Bz CT response in TRPV1 KO mice were inhibited to baseline level and were RTX-insensitive. In rats, blocking TRPV1 by capsazepine or TRPM5 by triphenylphosphine oxide inhibited the tonic NaCl + Bz CT response and shifted the relationship between RTX concentration and the magnitude of the tonic CT response to higher RTX concentrations. TRPM5 KO mice elicited no constitutive NaCl + Bz tonic CT response. The relationship between RTX concentration and the magnitude of the tonic NaCl + Bz CT response was significantly attenuated and shifted to higher RTX concentrations. The results suggest that pharmacological or genetic alteration of TRPM5 activity modulates the Bz-insensitive NaCl CT response and its modulation by TRPV1 agonists.

Topics: Amiloride; Anilides; Animals; Capsaicin; Chorda Tympani Nerve; Cinnamates; Diterpenes; Mice; Mice, Knockout; Organophosphorus Compounds; Rats; Rats, Sprague-Dawley; Sodium Chloride; Taste; TRPM Cation Channels; TRPV Cation Channels

Strain differences between naive, sucrose- and ethanol-exposed alcohol-preferring (P) and alcohol-nonpreferring (NP) rats were investigated in their consumption of ethanol, sucrose, and NaCl; chorda tympani (CT) nerve responses to sweet and salty stimuli; and gene expression in the anterior tongue of T1R3 and TRPV1/TRPV1t. Preference for 5% ethanol and 10% sucrose, CT responses to sweet stimuli, and T1R3 expression were greater in naive P rats than NP rats. The enhancement of the CT response to 0.5 M sucrose in the presence of varying ethanol concentrations (0.5-40%) in naive P rats was higher and shifted to lower ethanol concentrations than NP rats. Chronic ingestion of 5% sucrose or 5% ethanol decreased T1R3 mRNA in NP and P rats. Naive P rats also demonstrated bigger CT responses to NaCl+benzamil and greater TRPV1/TRPV1t expression. TRPV1t agonists produced biphasic effects on NaCl+benzamil CT responses, enhancing the response at low concentrations and inhibiting it at high concentrations. The concentration of a TRPV1/TRPV1t agonist (Maillard reacted peptides conjugated with galacturonic acid) that produced a maximum enhancement in the NaCl+benzamil CT response induced a decrease in NaCl intake and preference in P rats. In naive P rats and NP rats exposed to 5% ethanol in a no-choice paradigm, the biphasic TRPV1t agonist vs. NaCl+benzamil CT response profiles were higher and shifted to lower agonist concentrations than in naive NP rats. TRPV1/TRPV1t mRNA expression increased in NP rats but not in P rats exposed to 5% ethanol in a no-choice paradigm. We conclude that P and NP rats differ in T1R3 and TRPV1/TRPV1t expression and neural and behavioral responses to sweet and salty stimuli and to chronic sucrose and ethanol exposure.

Topics: Amiloride; Anilides; Animals; Central Nervous System Depressants; Chorda Tympani Nerve; Cinnamates; Dietary Sucrose; Diterpenes; Ethanol; Feeding Behavior; Food Preferences; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Biological; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Sodium Chloride, Dietary; Species Specificity; Taste Perception; Tongue; TRPV Cation Channels

The effect of ethanol on the amiloride- and benzamil (Bz)-insensitive salt taste receptor was investigated by the measurement of intracellular Na(+) activity ([Na(+)](i)) in polarized rat fungiform taste receptor cells (TRCs) using fluorescence imaging and by chorda tympani (CT) taste nerve recordings. CT responses were monitored during lingual stimulation with ethanol solutions containing NaCl or KCl. CT responses were recorded in the presence of Bz (a specific blocker of the epithelial Na(+) channel [ENaC]) or the vanilloid receptor-1 (VR-1) antagonists capsazepine or SB-366791, which also block the Bz-insensitive salt taste receptor, a VR-1 variant. CT responses were recorded at 23 degrees C or 42 degrees C (a temperature at which the VR-1 variant salt taste receptor activity is maximally enhanced). In the absence of permeable cations, ethanol induced a transient decrease in TRC volume, and stimulating the tongue with ethanol solutions without added salt elicited only transient phasic CT responses that were insensitive to elevated temperature or SB-366791. Preshrinking TRCs in vivo with hypertonic mannitol (0.5 M) attenuated the magnitude of the phasic CT response, indicating that in the absence of mineral salts, transient phasic CT responses are related to the ethanol-induced osmotic shrinkage of TRCs. In the presence of mineral salts, ethanol increased the Bz-insensitive apical cation flux in TRCs without a change in cell volume, increased transepithelial electrical resistance across the tongue, and elicited CT responses that were similar to salt responses, consisting of both a transient phasic component and a sustained tonic component. Ethanol increased the Bz-insensitive NaCl CT response. This effect was further enhanced by elevating the temperature from 23 degrees C to 42 degrees C, and was blocked by SB-366791. We conclude that in the presence of mineral salts, ethanol modulates the Bz-insensitive VR-1 variant salt taste receptor.

Topics: Amiloride; Anilides; Animals; Capsaicin; Cell Size; Central Nervous System Depressants; Chorda Tympani Nerve; Cinnamates; Cytosol; Diuretics; Ethanol; Female; Osmolar Concentration; Rats; Rats, Sprague-Dawley; Receptors, Drug; Sodium; Sodium Chloride; Taste; Temperature; Tongue

The effect of ethanol on the amiloride- and benzamil (Bz)-insensitive salt taste receptor was investigated by direct measurement of intracellular Na(+) activity ([Na(+)](i)) using fluorescence imaging in polarized fungiform taste receptor cells (TRCs) and by chorda tympani (CT) taste nerve recordings. CT responses to KCl and NaCl were recorded in Sprague-Dawley rats, and in wild-type (WT) and vanilloid receptor-1 (VR-1) knockout mice (KO). CT responses were monitored in the presence of Bz, a specific blocker of the epithelial Na(+) channel (ENaC). CT responses were also recorded in the presence of agonists (resiniferatoxin and elevated temperature) and antagonists (capsazepine and SB-366791) of VR-1 that similarly modulate the Bz-insensitive VR-1 variant salt taste receptor. In the absence of mineral salts, ethanol induced a transient decrease in TRC volume and elicited only transient phasic CT responses. In the presence of mineral salts, ethanol increased the apical cation flux in TRCs without a change in volume, increased transepithelial electrical resistance across the tongue, and elicited CT responses that were similar to salt responses, consisting of both a phasic component and a sustained tonic component. At concentrations <50%, ethanol enhanced responses to KCl and NaCl, while at ethanol concentrations >50%, those CT responses were inhibited. Resiniferatoxin and elevated temperature increased the sensitivity of the CT response to ethanol in salt-containing media, and SB-366791 inhibited the effect of ethanol, resiniferatoxin, and elevated temperature on the CT responses to mineral salts. VR-1 KO mice demonstrated no Bz-insensitive CT response to NaCl and no sensitivity to ethanol. We conclude that ethanol increases salt taste sensitivity by its direct action on the Bz-insensitive VR-1 variant salt taste receptor.

Topics: Algorithms; Amiloride; Anilides; Animals; Capsaicin; Cell Membrane; Cell Polarity; Central Nervous System Depressants; Chorda Tympani Nerve; Cinnamates; Diterpenes; Diuretics; Ethanol; Female; In Vitro Techniques; Mice; Mice, Knockout; Rats; Rats, Sprague-Dawley; Receptors, Drug; Sodium; Sodium Chloride; Stimulation, Chemical; Taste; Taste Threshold; Temperature; Tongue