Rats with area postrema lesions have lengthy eating and drinking bouts when fed ad libitum: implications for feedback inhibition of ingestive behavior

Ad libitum ingestive behavior of rats with area postrema lesions (APX) was monitored electronically every 6 s for 23 hr. Whereas control rats ate on average 32.2 g of food each day in 16.3 distinct bouts, rats with APX ate comparable amounts of food (28.6 g) in much fewer daily bouts (5.8) that were very large. Controls drank 38.4 ml of water daily in 17.8 bouts, whereas rats with APX consumed more than twice as much water (101.5 ml) in a similar number of bouts (18.5). Controls drank 5.3 ml of 0.5 M NaCl daily in 7.0 bouts, whereas rats with APX consumed 9 times as much saline (45.5 ml) in more bouts (18.2) that were relatively large. These and other results suggest that the area postrema plays an important role in detecting inhibitory signals generated by food or fluid intake and that feeding and drinking bouts may increase in size after APX, because the feedback inhibition provided by those signals is diminished.