Changes in respiratory quotient elicited in rats by a conditioned stimulus predicting food.
The present study examined whether changes in energy expenditure and energy substrate utilization occur in rats exposed to a conditioned stimulus that signals food. In a differential conditioning procedure, rats were given conditioning sessions where one of two cues (either a flashing light or buzzer) predicted a carbohydrate-rich meal (CS+) while the other cue predicted no food (CS-). In two subsequent test sessions, indirect calorimetry was used to measure respiratory quotient, energy expenditure, and locomotor activity before, during, and after a 15-min CS+ or CS- presentation. The CS+ was found to significantly increase respiratory quotient, indicating a shift in the energy substrate being utilized toward carbohydrate. The CS+ also increased energy expenditure and locomotor activity, but these effects were more variable across rats. It is concluded that respiratory quotient may rise in anticipation of a carbohydrate-rich meal. Possible mechanisms underlying this effect are discussed.
McGregor
I S
IS
Department of Psychology, University of Sydney, NSW, Australia. iain@psych.su.oz.au
Lee
A M
AM
D000818:Animals; D002153:Calorimetry, Indirect; D003214:Conditioning, Classical / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004435:Eating; D004734:Energy Metabolism / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration / Q000502:physiology*
D004040:Dietary Carbohydrates