On the relationship between sweet taste and seasonal body weight changes in a primate (Microcebus murinus)

Abstract

Abstract.The relationship between obesity and taste, especially sweet taste, has been and is of interest. From this point of view of a small primate, the lesser mouse lemur (Microcebus murinus), is of particular interest. It goes through a yearly cycle of physiological changes, one of which is an extreme variation in body weight of up to 100%. This occurs concomitantly with significant changes of the animal's liking for sucrose; measured by two-bottle preference tests, the threshold for sucrose changes from 28-45 in lean to 77-105 mM in obese animals. It is possible that a change in peripheral taste sensitivity might be the cause for these preference changes. To test this possibility we studied the ability of M. murinus to taste sucrose with electrophysiological and conditioned taste aversion techniques. The electrophysiological recordings were obtained from the chorda tympani proper nerve in two heavy and three lean animals. We did not record any difference between the two groups in their neural response to a series of sucrose concentrations. Conditioned taste aversion experiments with 200 mM sucrose as conditioning stimulus and 50 and 200 mM sucrose as test stimuli gave similar results. No difference was found between three heavy and four lean animals; both groups rejected the sucrose concentrations. The results support the notion that the seasonal variations in preference threshold to sucrose were unrelated to the ability of M. murinus to taste sucrose.

Sweet and Bitter Taste Discrimination in Primates: Scaling Effects across Species

“…Overall preference tests are in good agreement with evoked potentials recorded from the chorda tympani [11,12,24,27], demonstrating that species of the genera Eulemur, Saimiri and Macaca are able to taste lower concentrations of sucrose (10-30 mM) than the smaller species of the genera Microcebus and Saguinus (30-70 mM). A simple causal explanation for such relationships would be that, if tongue surface is positively related to body weight, the recruitment of a greater number of taste buds as body weight increases is sufficient to elicit a more intense signal.…”

Taste Perception of Fructose Solutions and Diet in Lemuridae

“…It is surpris ing that a very high taste threshold for fruc tose was found (100-119 mM ), whereas a re sponse of the chorda tympani was recorded for sucrose concentrations as low as 10 mM in this species [16]. Further data are needed to determine whether such a difference reflects an actual differential sensitivity towards sug ars or merely reflects the atypical response of a single individual.…”

“…On the one hand, there is evidence based on investi gations of three primate species [10,11] that both the two-bottle test and the electrophysiological recording of the evoked firing activity of the chorda tympani nerve yield similar taste thresholds for sucrose. On the other hand, it has been demonstrated that the 'be havioural threshold' for sucrose of Microcebus murinus (Cheirogaleidae) varies seasonal ly, with no concomitant change in the re sponse of peripheral nerves [8,12]. Accord ingly, the possibility that taste thresholds for fructose of lemurs mainly reflect motivational aspects of feeding behaviour, as in M. murinus, cannot be ruled out.…”

Taste Difference Thresholds for Sucrose in Squirrel Monkeys (Saimiri sciureus)

“…Firstly, the interindividual variability found in humans spans a range from 0.125 to 0.5 for the JND for sucrose [8], and although the animals here showed very little interindividual difference in performance, factors such as nutritional state [10] and seasonality of physiological pa rameters [11] may influence gustatory sensi tivity in primates. Secondly, while the JND for humans has been established using sophis ticated signal detection methods, the two-bot tle preference test provides only a conserva tive approximation of a species' limits of gus tatory capacity.…”