The influence of gastrointestinal infusions of glucose on regulation of food intake in pigs.

The influence of gastrointestinal infusions of glucose on short-term and 24 h control of food intake was studied in sixteen pigs fed twice per day and nine fed three times per day. The pigs were fitted with up to four catheters each, placed in the stomach, the duodenum and at 2 and 8 m from the ligament of Treitz (l.t.). Infusions were given into the catheters, beginning 30 min before the first meal (two feeds) or second meal (three feeds) of the day, and continuing until the pigs stopped eating. The effects of the infusions on both short-term and 24 h intakes were the same whether the pigs were given two or three feeds per day. Infusions of glucose (400 g/l) into the stomach or small intestine altered short-term (meal) intake, but had no effect on intake at the following meal. With glucose infusion at rates above a threshold level (4 ml/min) to the stomach, duodenum or ileum (8 m from l.t.) food intake at that meal was suppressed such as to compensate for the amount of energy infused. Glucose infusions to the jejunum (2 m from l.t.) caused greater inhibition of short-term intake than infusions elsewhere, and 6 ml/min glucose inhibited intake by more than the amount of energy infused. Duodenal injection of the local anaesthetic lignocaine markedly suppressed the inhibition of intake caused by gastric infusion of glucose. The reductions in intake with glucose infusions at various rates into the stomach or duodenum were nearly identical to those with the same rates of infusion of NaCl at the same high osmolarity. It is concluded that glucose activation of receptors over a large part of the small intestine participates in the short-term control of energy intake in the pig, and that the receptors are activated equally by glucose in terms of an osmotic or caloric stimulus. It is suggested that activation of these receptors is involved in the caloric regulation of gastric emptying leading to gastric distension and inhibition of further intake.