The Effect of Centrally Administered Glibenclamide, Tolbutamide and Diazoxide on Feeding in Rats

Evidence for hypothalamic KATP+ channels in the modulation of glucose homeostasis

Several lines of evidence support the hypothesis that ATP-sensitive K+ channels (K+(ATP)) participate in the brain's regulation of peripheral glucose homeostasis. In testing this hypothesis we conducted a series of in vivo experiments using albino rats and bilateral intrahypothalamic injections of K+(ATP) channel blockers, glibenclamide and repaglinide. The results show that 0.2 and 2.0 nM injections of glibenclamide lowered blood glucose in a dose-dependent manner. During mild insulin-induced hypoglycemia, hypothalamic glibenclamide delayed recovery to normoglycemia. The impaired recovery was associated with a reduction in plasma norepinephrine (P<0.001), though circulating epinephrine and glucagon were not reduced. In a separate experiment, 2-deoxy-D-glucose (200 mg/kg) was intraperitoneally administered to produce neuroglucopenia. Hypothalamic injections of either glibenclamide or repaglinide significantly blunted compensatory hyperglycemic responses (P<0.01). In a feeding study, 2.0, but not 0.2 nM of hypothalamic glibenclamide, reduced chow intake over a 2-h period (P<0.01). The results support the hypothesis that hypothalamic K+(ATP) channels participate in central glucose-sensing and glucose regulation.

Hydroxyl-substituted sulfonylureas as potent inhibitors of specific [3H]glyburide binding to rat brain synaptosomes

We are seeking to discover potent CNS-active sulfonylureas with structural features that allow for the formation of several types of prodrugs. We report herein the syntheses of compounds comprising an initial series of hydroxyl-substituted analogues of the potent ATP-sensitive potassium channel blockers glyburide (glibenclamide) and gliquidone. Somewhat unexpectedly, several of the compounds were found to be comparably potent to glyburide as inhibitors of specific [(3)H]glyburide binding in rat brain preparations.

Glibenclamide's action in the hypothalamus alters peripheral glucose homeostasis

Bilateral injections of 0.2 nmol of glibenclamide, targeted at the ventromedial hypothalamus of albino rats, significantly impaired recovery of blood glucose levels following insulin-induced hypoglycemia (P=0.0026). Similar injections of 0.2 and 2.0 nmol glibenclamide reduced blood glucose by 23.6 and 40.8 mg%, respectively, in otherwise untreated rats (P<0.01 and P<0.001). Intravenous injection of these doses of the drug did not lower blood glucose. The results support the hypothesis that K(ATP)(+) channels within the hypothalamus serve a counterregulatory function in the maintenance of peripheral glucose levels.