TASTE PREFERENCE AND SENSITIVITY: EFFECTS OF CHOLECYSTOKININ AND LEVEL OF FOOD DEPRIVATION.

Abstract

Several feeding-related factors can affect taste sensitivity or preferences and therefore may be part of a homeostatic regulatory mechanism. Cholecystokinin (CCK), a hormone which reduces food intake in several species, has also been postulated to interact with the orosensory characteristics of food. To test this hypothesis, the effects of CCK-8 and food deprivation on the short-term intakes of water, sucrose solutions (0.05 to 1.0 M), and saline solutions (0.05 and 0.15 M) were determined. In most cases, CCK (2 μg/kg) reduced sucrose intake when measured either as the amount consumed or the number of licks in a short period (nine minutes). Additionally, CCK reduced the intake of 0.15 M NaCl in satiated rats and water intake in both hungry and satiated rats. Rats usually consumed more sucrose when hungry than when satiated or fed ad libitum; CCK-induced suppression of intake, however, was generally greater in the satiated or ad libitum conditions than in the hungry condition. There was no systematic effect of sucrose concentration on the amount of CCK-induced suppression of intake, which suggests that CCK regulates rather than interferes with ingestion. To determine whether the CCK-induced suppression is due to a change in the peripheral taste signal, the integrated chorda tympani responses to sucrose and NaCl tastes were recorded in rats anesthetized with either urethane, Innovar-Vet, or a combination of urethane and alpha-chloralose. The only significant effect of CCK was the slight increase in the initial response to 0.3 M sucrose after the infusion of a total of 10 μg of CCK-8 into rats anesthetized with Innovar-Vet. In general, therefore, the effect of CCK on sucrose intake does not appear to be due to a peripheral taste change; an analysis of single taste fibers, however, would be more conclusive. An examination of the effects of CCK on central gustatory and reward areas might yet provide a mechanism for the CCK effect on taste-motivated ingestion.