Effect of food restriction on acquisition and expression of a conditioned odor discrimination in mice

Level of food restriction was manipulated in mice to assess its importance for the acquisition and expression of a conditioned odor discrimination. In training, animals were exposed to odors (either rose or lemon) presented o n a piece of filter paper in a pot covered in bedding. For half of the cond itioning trials, group paired received one odor (CS+) with sucrose, the unc onditioned stimulus (US), under the bedding. For the remaining trials, they received the other odor (CS-) alone. Group CS-alone was also exposed to bo th odors, but neither odor was paired with sugar on any of the conditioning trials. During training, Group Paired mice that were food-restricted tende d to dig more readily and longer in the odors, especially in the CS+ odor, than animals that were not restricted. Both restricted and nonrestricted PA IRED GROUPS dug more in the CS+ than in the CS- by the end of training, but the CS-alone mice dug very little in either. Following training, mice were exposed to both odors simultaneously in a discrimination test. Half the mi ce in each training food restriction condition were tested under food restr iction, and half were not. Only PAIRED animals that were food-restricted in the test expressed an odor discrimination, digging only in the CS+.. This occurred regardless of their previous restriction state in training. These data suggest that both food-restricted and nonrestricted mice can acquire a n odor discrimination; however, expression of this odor discrimination depe nds on food restriction. (C) 2001 Elsevier Science Inc. All rights reserved .