Conditioned taste aversion learning in leptin-receptor-deficient db/ db mice

• Published in: Neurobiology of learning and memory Vol. 80; no. 2; pp. 105 - 112
• Main Authors: Ohta, Rie, Shigemura, Noriatsu, Sasamoto, Kazushige, Koyano, Kiyoshi, Ninomiya, Yuzo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.09.2003; Elsevier
• Subjects: Animal; Animals; Behavior, Animal - physiology; Biological and medical sciences; Choice Behavior; Conditioned taste aversion; Conditioning; Conditioning (Psychology) - physiology; db/ db mice; Female; Fundamental and applied biological sciences. Psychology; Learning; Learning. Memory; Leptin-resistance; Male; Mice; Mice, Inbred C57BL; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Receptors, Cell Surface - deficiency; Receptors, Leptin; Taste - physiology; Learning; db/ db mice; Leptin-resistance; Conditioned taste aversion; Feeding behavior; Sucrose; Rodentia; Experimental study; Generalization; Alimentary aversion; Vertebrata; Saccharin; Mammalia; Acquisition process; Mouse; Food intake; Animal; Leptin; Taste; Extinction curve; Conditioned aversion; Biological receptor
• ISSN: 1074-7427; 1095-9564
• DOI: 10.1016/S1074-7427(03)00046-7

The db/ db mouse has defective leptin receptors. The defects lead to impairments of leptin regulation of food intake and body weight, and result in the expression of diabetic symptoms such as hyperinsulinemia, hyperglicemia, and extreme obesity. Recent studies have proposed that leptin may also affect memory and learning processes. To examine this possibility, we compared the ability of leptin-receptor-deficient db/ db mice and their normal lean litter mates to form and extinguish a conditioned taste aversion (CTA) for saccharin. We used a short-term (10 s) lick test and a long-term (48 h) two bottle preference test for measurement of consumption of test solutions. On the first day after conditioning to avoid saccharin, the db/ db mice showed preference scores for saccharin as low, and aversion thresholds for sucrose lower than that of the lean mice. During the extinction test trials beginning from the second up to the 30th day after conditioning, numbers of licks and preference scores for aversive saccharin and sucrose appeared to be larger, and recovered faster to the control levels in db/ db mice. These results indicate that db/ db mice with leptin-receptor-deficiency may show equal capacity to form CTAs for saccharin, greater generalization from saccharin to sucrose, and a faster rate of extinction. This suggests that disruption of leptin signalling does not inhibit acquisition of CTA learning, but impairs its extinction. This differential contribution of the leptin system on CTA processes may be due to differential distribution of leptin receptors in the CTA-related brain areas.