Effects of insulin and 2-deoxy-D-glucose on plasma glucose level and lateral hypothalamic eating threshold in the rat

Thresholds for elicited eating through monopolar electrodes in the perifornical region of the lateral hypothalamus and plasma glucose concentration were determined over periods of several hours, while blood glucose levels and cellular glucose utilization were altered by means of forced feeding through hypothalamic stimulation, subcutaneous insulin injections and/or intraperitonneal 2-deoxy-D-glucose injections. Forced feeding resulted in increased thresholds for elicited eating, whereby the plasma glucose concentration in the tail vein was positively correlated to these thresholds. A subsequent, long-lasting, severe insulin-hypoglycemia was not sufficient to normalize such elevated thresholds. However, 2-deoxy-D-glucose in doses of 100–250 mg/kg, after an initial increase, decreased thresholds 90 min after injection. When insulin and 2-deoxy-D-glucose were combined so as to balance the contrary glycemic effects, the insulin effect dominated, resulting in slightly increasing thesholds. The results are discussed in terms of the recently suggested hypothesis that insulin regulates glucose entry into glucosensitive systems of the ventromedial hypothalamus, and thus generates satiety signals rather than hunger.