INFLUENCE OF INSULIN INJECTIONS AND INFUSIONS ON EATING AND BLOOD GLUCOSE LEVEL IN RAT

The effect of insulin on blood glucose and food intake in unanesthetized rats was studied under two conditions: (a) after a single intravenous injection of insulin; (b) during continuous insulin infusion over 9 hr. Insulin was given and blood samples were taken without disturbing the animals by means of a double intracardial catheter. After a single injection blood glucose declines steeply to 50 mg% and remains at a plateau until a meal starts, then a sudden rise ensues. Continuous infusion of insulin in normal rats induces hyperphagia: blood glucose decreases slowly to 50 mg%; at which point a meal begins, a sudden rise in glucose ensues, followed by slow return to 50 mg%. This cycle is repeated continually. Identical infusions of insulin into static obese hypothalamic subjects (whose daily food intake is fairly normal) leads to renewed hyperphagia, but the fluctuations in blood glucose that accompany the meal cycle are much reduced in amplitude as compared to normal rats under the same treatment. © 1969.