Feeding dynamics: How rats regulate eating when food is unavailable for unpredictable amounts of time

.- B.S. ZANUTTO, J.E.R. STADDON

San Diego, USA

Congreso; 31st Annual Meeting of the Society for Neuroscience.; 2001

Society for Neuroscience.

 We used a simple dynamic model to simulate the effects on subsequent eating of making food unavailable for unpredictable amounts of time and compared the predictions with experimental data from rats. The model assumes that feeding is turned off and on by a satiation signal (SS), which is a delayed after-effect of eating. Feeding occurs (if food is available) only when the SS falls below a set point. In a series of experiments, six male Sprague Dawley rats, 45 days old, were individually housed in cages at 23 °C, with a drinking tube, a food-cup with a 45-mg pellet dispenser and, a running wheel. If the rat´s head entered an empty food cup, a pellet was dropped; if the pellet was not eaten after 10 minutes, it was removed. The first 3 days the rats had free access to food to habituate them to the apparatus. From the 4th day, free-feeding was interrupted once per night. The interruption began at three fixed random times (e.g. 10 PM, 1 AM or 4 AM) after the animal put its head inside the food-cup to initiate a new meal. The interruption was chosen randomly to be 1,2 or 3 hours long. When the interruption period terminated, a new pellet was dropped and a red signal light was turned on. We found that the first meal after the interruption is longer than the preceding and the successive meals. Since these data as well as published data in rats agree quantitatively with the predictions of the model, we conclude that the basic dynamics of both free and constrained feeding in closed economies are the result of a negative-feedback process in which the satiating effects of food are delayed after ingestion.