Antagonism of the gerbil's sweetener and Polycose gustatory responses by copper chloride

Antagonism of the gerbil's whole chorda tympani nerve taste responses by CuCl2 was studied. A 30 min pretreatment of 0.1 mM CuCl2 suppressed responses to single concentrations of the following sweeteners: L-alanine, L-proline, D-tryptophan, 6-chloro-D-tryptophan, L-valine, glycine, sucrose, maltose, lactose, tetrachloro-galacto-sucrose, glucose, fructose, methyl alpha-D-glucopyranoside, glycerol, sorbitol, sodium saccharin, L-4'-cyano-3'-(2-2-2-trifluoro acetamido)succinanilic acid, phenethyurea, and stevioside. The responses to L-serine and the starch hydrolysate, Polycose were depressed to a lesser degree. The responses to glycine HCl and NaCl were slightly suppressed by CuCl2. The 0.1 mM CuCl2 had no effect on the shape of the sucrose concentration-response curve or its 1/2 maximal response (CR50), but did suppress the maximum response (Rmax), characteristic of non-competitive antagonism. Our work suggests the presence of 2 separate receptor sites on the gerbil's taste receptor cell membrane, one of which interacts with sugar sweeteners and most other non-sugar sweeteners and the other with Polycose.