Stimulation of the gerbil's gustatory receptors by polyols

Single neuron gustatory responses of the gerbil chorda tympani to a variety of stimuli (recorded by a new method)

In most mammalian studies on gustatory single neuron recordings, the animal's chorda tympani nerve was cut and manipulated. This results in nerve trauma which may have affected the precision of the responses. In this paper, we are presenting a method whereby gustatory recordings were obtained from gerbil single chorda tympani neurons by inserting a microelectrode directly into the uncut nerve. The stimuli included 0.3 M NaCl, 0.3 M KCl, 0.3 M CaCl2, 0.3 M NH4Cl, 0.05 M acetic acid, 0.01 M quinine HCl, 32% Polycose and the sweeteners 0.5 M D-glucose, 0.5 M D-fructose, 0.02 M sodium saccharin and 0.5 M sucrose. While thirty-seven of the sixty seven neurons tested did not respond to any of the eleven gustatory stimuli applied to the gerbil's tongue, thirty positive single neuron responses were obtained to this group of compounds. The thirty positive neuron responses were grouped in two ways: (1) by observationally sorting the data according to maximum responses to four stimuli, sucrose, NH4Cl, NaCl, and acetic acid; and (2) by objectively sorting the data matrix using cluster analysis. The groups resulting from each method were then characterized and compared by discriminant function analysis. By the first grouping method, ten neurons responded best to sodium chloride, seven to acetic acid, four to ammonium chloride, and nine to sucrose. However, canonical discriminant function analysis showed that two of the four groups, acetic acid and ammonium chloride, occupied the same region of discriminant space and should be combined.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The gerbil: a unique model for research on aging

The Mongolian gerbil (Meriones unguicultatus) is suggested as a model for aging research because of its unique physiological attributes, ease of handling, and because of data previously collected. Factors that demonstrate the gerbils' suitability in fulfulling practical and scientific considerations important in determining a model for aging research are listed. Additionally, several unique physiological attributes of gerbils are described. Based on these attributes and on review of research in gerbils, it is suggested that gerbils can serve as animal models for behavioral and biological processes, and for normative and pathological aspects for aging.

Methyl 4,6-dichloro-4,6-dideoxy-alpha-D-galactopyranoside: an inhibitor of sweet taste responses in gerbils

The sugar methyl 4,6-dichloro-4,6-dideoxy-alpha-D-galactopyranoside (DiCl-gal) is a new type of inhibitor of the gerbil's electrophysiological taste response to sucrose or saccharin. Saturated solutions of this compound alone barely stimulate the gerbil's taste nerve. But, when mixed with sucrose or saccharin, DiCl-gal suppresses the gerbil's taste response to these two sweeteners. In contrast, when mixed with sodium chloride or hydrochloric acid, DiCl-gal does not affect the taste responses to these compounds. However, unlike other inhibitors of sweet taste, the DiCl-gal taste suppression is short-lived and occurs only when the inhibitor is combined with the sweetener.

Taste aversion to sugars by the gerbil

Some conditioned taste aversion experiments were undertaken to determine how the gerbil responds to disaccharides, monosaccharides and polyols. We observed the following: animals taught an aversion to 0.1 M sucrose generalized the avoidance to most sugars, the exception being galactitol; animals taught to avoid 0.01 M hydrochloric acid generalized the avoidance towards lactose, cellobiose, maltitol, methyl alpha-D-galactopyranoside, methyl alpha-D-mannopyranoside, methyl beta-D-glucopyranoside, and glycerol; animals taught to avoid 0.001 M quinine . HCl generalized the avoidance towards methyl alpha-D-glucopyranoside, methyl-beta-D-glucopyranoside, glycerol, ethylene glycol and erythritol. In no case did animals taught to avoid 0.1 M sodium chloride avoid any of the sugars. Moreover, it was observed that the gerbil's behavior with most reducing sugars was different than with equivalent methyl glycosides. For example, animals that were taught to avoid sucrose generalized the avoidance towards reducing sugars, such as, D-galactose, D-glucose, and D-mannose. However, the methyl glycosides, such as methyl alpha-D-glucopyranoside, methyl beta-D-glucopyranoside, methyl alpha-D-galactopyranoside and methyl alpha-D-mannopyranoside, in addition to being avoided by animals taught to avoid sucrose, were also avoided by animals taught to avoid quinine . HCl or hydrochloric acid. In addition, we have observed that the control animals consumed differing amounts of sugars and have concluded, therefore, that the sugars were not equally pleasant despite our attempt to use concentrations which produced equally intense neural responses in the gerbil's chorda tympani nerve.

Stimulation of the gerbil's gustatory receptors by artificial sweeteners

Some electrophysiological and behavioral taste experiments have been undertaken to determine how the Mongolian gerbil responds to artificial sweeteners. In the electrophysiological experiment only fourteen of twenty-one sweeteners produced neural responses. The most potent compound was L-4'-cyano-3-(2,2,2-trifluoroacetamido)succinanilic acid. Halogenated derivatives were more potent stimuli than non-halogenated ones. D-Tryptophan was stimulatory while L-tryptophan was not. The electrophysiological responses to sucrose were not inhibited by the presence of non-stimulating sweeteners nor were the responses to D-tryptophan inhibited by L-tryptophan. All the compounds that were stimulatory electrophysiologically were used in the behavior experiment. Using conditioned taste aversion, the gerbils responded to 5 of the compounds as sweet, one as sweet-salty, two as sweet-bitter, one as sour and one as bitter. In addition, 3 compounds were drunk equally by all groups suggesting that they were tasteless or possessed some unknown taste quality. A correlation was found between the efficacy (Kd) of the sweet-tasting compounds (pure sweet or mixed sweet) and the sweetness ranking by humans.