Effects of running wheel activity on the sensory and metabolic regulation of food intake

Abstract

Three experiments designed to investigate running as a form of major energy expenditure or energy regulation in relation to food intake are reported. The first and second experiments examined whether running wheel activity has a differential modulating effect on the sensory-metabolic system which presumably controls how rats respond to altered taste or caloric properties of food. Active and nonactive Ss were presented with 0.02% quinine adulterated or 40% diluted liquid diets following ad libitum feeding and 24 hours of food deprivation. Both active and nonactive Ss increased intake of the diluted diet following ad libitum feeding and food deprivation, apparently responding to the decreased caloric content. Although there was an increase in amount consumed, caloric intake decreased. When presented with the quinine adulterated diet following ad libitum feeding, only the active Ss reduced intake significantly. This reduction in caloric intake was accompanied by an increase in running activity. All Ss increased consumption of the quinine diet following food deprivation. Only the active, ad libitum Ss responded to the aversive taste properties of the quinine diet. When food-deprived, all Ss responded to the caloric properties of the diluted and quinine diet, apparently ignoring the aversive taste. The third experiment was designed to determine how active Ss would respond to the normal liquid diet, the diluted diet, and the quinine adulterated diet when access to the running wheel was removed. All Ss increased caloric intake of the three test diets during the 24-hour test period of wheel removal, but quinine consumption was not significantly greater than the baseline measure. The results were discussed in terms of two theoretical positions regarding running activity: (1) running as a form of major energy expenditure, where the state of relative energy balance determines how an animal will respond to altered taste or caloric properties of food, and (2) running as a means of behavioral regulation of available energy stores. The adequacy of inferences about energy balance and energy regulation was also discussed.