Role for epithelial Na⁺channels and putative Na⁺/H⁺exchangers in salt taste transduction in rats

Abstract

The effects of the epithelial Na+channel antagonists amiloride and benzamil and the Na+/H+exchange antagonist 5-( N, N-dimethyl)-amiloride (DMA)-Cl on the integrated responses of the chorda tympani nerve to 30, 75, 150, 300, and 500 mM concentrations of NaCl, KCl, and NH4Cl were assessed in male Sprague-Dawley rats. Based on evidence from other systems, 1 and 25 μM amiloride and benzamil were chosen to selectively inhibit epithelial Na+ channels and 1 μM DMA was chosen to selectively inhibit Na+/H+exchange. When added to stimulating salt solutions, amiloride, benzamil, and DMA were each effective in inhibiting responses to all three salts. The degree of inhibition varied with drug, salt, and salt concentration, but not drug dose. Amiloride suppressed NaCl responses to a greater degree than KCl and NH4Cl responses, whereas DMA suppressed NH4Cl responses to a greater degree than NaCl and KCl responses. In all but one case (25 μM amiloride added to KCl), drug suppression of taste nerve responses decreased with an increase in salt concentration. The present results suggest that 1) epithelial Na+ channels in rat taste receptor cells may play a role in KCl and NH4Cl taste transduction; 2) a Na+/H+exchange protein may be present in taste receptor cells, representing a putative component, in addition to epithelial Na+ channels, in salt taste transduction; and 3) salt taste detection and transduction may depend on the utilization of a combination of common and distinct transcellular pathways.

Sensitive periods for the effect of dietary sodium restriction on intact and denervated taste receptor cells

“…Moreover, in the current experiments, decreased responses to HCl were observed even in groups that did not exhibit changes in responses to sodium. Perhaps sodium restriction and/or unilateral CT section influence acid transduction through proton channels, the Na ϩ -H ϩ exchanger, or the intracellular pH of taste receptor cells (26)(27)(28)40).…”

Ontogeny of urine preference and its relationship to NH4Cl preference and sodium hunger in suckling rat pups

“…Neurophysiological studies confirm the distinction between the two salts (Hill & Mistretta, 1990;Kitada, Mitoh, & Hill, 1998;Lundy, Pittman, & Contreras, 1997) and suggest that the parabrachial nucleus may mediate the neural and behavioral responses (Nishijo & Norgren, 1997).…”

Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System

“…35 Although amiloride is not a specific inhibitor of DEG/ENaC channels, it can also inhibit other membrane transport processes. Amiloride-insensitive mechanisms have also been proposed to participate in mammalian NaCl taste and include Na/H antiporters 36 and cation diffusion through tight junctions. 29 Drosophila genome has a large number of predicted DEG/ ENaC genes, 37 and these channels have been later tested for their role in salt taste.…”