Effects of Gastrointestinal Surgery on Ingestive Behavior in Animals

Abstract

Surgical manipulations of the gastrointestinal system can have a major impact on the ingestive behavior of animals. Particularly well-documented are the feeding and drinking effects of JIB and vagotomy. These two surgical procedures are similar in that they reduce the food intake and body weight of obese animals more than that of lean animals, and of hypothalamic obese rats more than that of genetically obese rats. Intermediate effects are obtained with other obesity models. Given the multiple etiologies of human obesity, it is not surprising that gastrointestinal surgery has variable effects in obese humans. The effects of gastric surgery on the ingestive behavior of animals have received relatively little attention. This is unfortunate because gastric bypass is now one of the most widely used methods for surgical treatment of human obesity. In light of recent developments in gastric surgical techniques and new findings concerning the gastric modulation of food intake, the effects of gastric surgery on the feeding behavior of animals should be further investigated. Much remains to be learned about the physiologic and behavioral mechanisms by which gastrointestinal surgery influences ingestive behavior and body weight. Surgical manipulations of the gastrointestinal system may affect ingestive behavior by directly altering the neural and hormonal feedback signals to the brain from the stomach, intestines, and other organs (liver, pancreas), or they may indirectly alter these feedback signals by modifying the preabsorptive and/or postabsorptive flow of nutrients. Seen from a functional perspective, the gut sends to the brain different types of messages that modulate ingestive behavior. Most attention has focused on gut satiety signals, but the gut can also be the source of painful sensations that suppress ingestive behavior. The distinction between satiety and discomfort is not always clear-cut. For example, gut distention may be satiating when it is moderate, but painful when it is extreme. Nevertheless, the distinction is an important one, and the nature of the feeding-inhibitory effects obtained in animal studies must be carefully evaluated. Ideally, obesity surgery should produce minimal aversive consequences, although whether it is possible to reduce food intake and body weight without producing any discomfort remains to be established. In addition to being a source of feeding-inhibitory cues, the gastrointestinal system may also provide excitatory cues that stimulate feeding and modify food preferences. For example, intestinal infusions of carbohydrates increase subsequent food intake under certain conditions.(ABSTRACT TRUNCATED AT 400 WORDS)