Modulation of behavioral and insulin responses by contextual stimuli paired with food

A context-like conditioned stimulus (CS) previously paired with a food unconditioned stimulus (US) enhanced both food-related activity and insulin secretion in rats. Experiment 1 documented the effectiveness of an appetitive conditioning procedure in which a 10 sec visual CS ("x") was followed by food when embedded within one 35 sec auditory CS ("A"), but not another ("B"). Approach to a food magazine during x was enhanced (facilitated) when x was within A, as compared to within B or alone. Experiment 2 documented the adequacy of blood sampling and insulin assay procedures that could be accommodated to the conditioning procedure. Plasma insulin was observably different after unconditioned deliveries of glucose solutions of different intensities. In Experiment 3, training as in Experiment 1 was followed by testing for food magazine approach and changes in insulin levels following x alone or in the presence of A or B. It was demonstrated that the A cue enhanced both responses. The results support the view [e.g., (18,19)] that insulin secretion is in part under the control of environmental cues, and findings (22) that show that conditioned context-like cues can modulate consummatory responding to punctate CSs.