Behavioural energy regulation in lean and genetically obese (ob/ob) mice

The role of behaviour in the control of energy regulation has been investigated in relation to environmental temperature, nutrition and genetics. Techniques of operant conditioning were used, with lean and genetically obese (ob/ob) mice being tested at three environmental temperatures (10, 20 and 30 degrees C) and on two feeding regimes (after a 24 hr fast and after feeding ad lib). They were allowed access to heat and food, although the design of the apparatus ensured that both were not available simultaneously. Both the lean and ob/ob showed an initial preference for heat when tested in a cold environment. At a low ambient temperature the ob/ob were dependent on the heater rather than food to increase rectal temperature, both when fasted and when fed. By contrast, the lean had a lower demand for heat than the obese and used the time to explore the environment and to feed. Food intake increased with an increase in ambient temperature in both genotypes. Possible reasons for this are discussed.