Self-Inhibition in Ca-Evoked Taste Responses: A Novel Tool for Functional Dissection of Salt Taste Transduction Mechanisms

Kloub, Mamoun A., Gerard L. Heck, and John A. DeSimone. Evidence suggests that the amiloride-insensitive component Self-inhibition in Ca-evoked taste receptors: a novel tool for (AIC) of the NaCl neural response arises from transduction functional dissection of salt taste transduction mechanisms. J. Neusites along the basolateral membranes of receptor cells, acrophysiol. 79: 911–921, 1998. Rat chorda tympani (CT) responses cess to which is assumed to be through paracellular pathways to CaCl2 were obtained during simultaneous current and voltage (Elliot and Simon 1990; Mierson et al. 1996; Simon et al. clamping of the lingual receptive field. Unlike most other salts, 1993; Stewart et al. 1995; Ye et al. 1993). The principal CaCl2 induced negatively directed transepithelial potentials and barriers in these pathways are the TJs that connect the apical gave CT responses that were auto-inhibitory beyond a critical conpoles of the taste receptor cells, which act as weakly cationcentration. CT responses increased in a dose-dependent manner to Ç0.3 M, whereafter they decreased with increasing concentration. selective barriers (DeSimone et al. 1984; Simon and Garvin At concentrations where Ca was self-inhibitory, it also inhibited 1985; Ye et al. 1993). In addition, these pathways likely responses to NaCl, KCl, and NH4Cl present in mixtures with CaCl2 . participate in K and NH 4 salt taste responses (Kloub et Ca completely blocked the amiloride-insensitive component of al. 1997; Ye at al. 1994). If so, transduction sites for NaCl, the NaCl CT response, the entire KCl-evoked CT response, and KCl, and NH4Cl may be accessible only by means of a the high-concentration-domain CT responses of NH4Cl (¢0.3 M). common pathway across the TJ complex. However, until The overlapping Ca-sensitivity between the responses of the now, a reliable means of probing paracellular pathways, inthree Cl salts (Na , K , and NH4 ) suggests a common, Cavolved in taste reception, has been unavailable. sensitive, transduction pathway. Extracellular Ca has been shown