SYMPATHETICALLY-MEDIATED THERMOGENIC RESPONSE TO FOOD IN RATS

The aim of this work was to assess the participation of the sympatheti c nervous system in the thermogenic response to food in control and hy perphagic rats. Rats were fed either a control (CD) or energy dense (E D) diet. After 15 days, CD rats received a small (7 kJ) meal composed of either control or energy dense diet, while ED rats received a small meal composed of energy dense diet. The experiment was then repeated, with the exception that rats received a larger portion (35 kJ) of the test meal. The postprandial increase in oxygen consumption was measur ed for 30 min after the small meal and 90-180 min after the completion of the large meal. The measurements were made in saline-injected and propranolol-injected rats. ED rats exhibited hyperphagia as well as an increase of 32% in resting metabolic rate after a 16 h fast. The symp athetically-mediated postprandial increase in oxygen consumption was g reater after an energy dense meal than after a control meal in CD rats , and was higher in ED rats than in CD rats fed an energy dense meal. It was concluded that the sympathetically-mediated increase in the the rmogenic response to food, as well as the increase in fasting metaboli c rate can help prevent obesity development in hyperphagic rats.