POSTPRANDIAL THERMOGENESIS AND CONDITIONED TASTE-AVERSION OR PREFERENCE

Postprandial thermogenesis is under the control of the autonomic nervo us system and alimentary conditioned stimuli change sympathetic and pa rasympathetic activity. Here we studied the effect of conditioned tast e aversion on postprandial thermogenesis in rats. Two groups of animal s were used, rats of the first group were controls, these were placed on a standard diet and, for some days, on two other different diets: o ne thiamine-free and the other thiamine-rich. Each diet had a differen t taste. The treated animals belonged to the second group, these were fed with the same three diets but for different lengths of times: thia mine-free diet for the first 5 wk afterwards, with thiamine-rich diet for 3 wk, and finally with laboratory standard diet for a few days. Af ter a preference test with the three familiar diets, oxygen consumptio n rate and brown adipose tissue temperature were evaluated three times in both groups after ingestion of a test meal, each time with one of the three different diets. The preference test was unvaried for the th ree different familiar foods in controls, while the treated animals sh owed a lower preference for thiamine-free food than for the other two. Treated rats had a significantly higher increase in O-2 consumption r ate than controls. In this group intake of thiamine-free food induced a significantly lower increase in O-2 consumption than the other two. The increase in brown adipose tissue temperature was also higher in tr eated than in control animals but in treated rats this was lower after intake of thiamine-free food than after the intake of the other two. The higher rise in postprandial thermogenesis in treated rats and the lower response found after intake of an aversive meal is probably due to changes in the autonomic nervous and of endocrine systems.