Hyporesponsiveness to glucoprivation during postnatal period in the rat

2-Deoxy-D-glucose (2-DG), a glucose analogue, blocks glycolysis and induces intracellular glucoprivation. In the adult rat intraperitoneal administration of 2-DG or its injection into the lateral ventricle (IVT) of the brain induces hyperglycemia which is divorced from a rise in plasma insulin (IRI). In the present study, responsiveness to 2-DG-induced glucoprivation, after central or intraperitoneal injection of the drug, was studied in rats of 7, 14, 21, and 28 days of age and compared to that of the adult rat (50 days old). In 7-, 14-, 21-, and 28-day-old rats, the overall blood glucose (BG) response to IVT-injected 2-DG was equivalent to 4, 3.3, 17, and 33%, respectively, of the BG response present in the adult rat. Following intraperitoneal injection of 2-DG , the BG response evoked in the same age groups corresponded to 27, 31, 41, and 93%, respectively, of the adult response. Base-line plasma IRI levels were significantly lower in pups than in adults and increased progressively with age, but no difference was present in IRI levels between 2-DG-treated and control pups whether the 2-DG was given via the laterl ventricle or intraperitoneally. These results demonstrate the presence in the infant rat of clear-cut hyporesponsiveness to 2-DG-induced glucoprivation. The different response pattern between experiments involving central and peripheral 2-DG administration supports the existence of separate peripheral glucoreceptors for 2-DG and their earlier ontogenic activation. Since the infant mammal glucose is of minor relevance as an energy substrate, an interrelationship appears to be present between requirements for fuel(s) and homeostatic response to fuel deprivation.