Similar to insulin, central administration of insulin-like Growth Factor-1 (IGF-1) can suppress hepatic glucose production (HGP), but it is unclear if this effect is mediated via insulin receptors (InsRs) or IGF-1 receptors (IGF-1Rs) in the brain. To this end, we utilized pharmacologic and genetic approaches in combination with hyperinsulinemic-euglycemic clamps to decipher the role of these receptors in mediating central effects of IGF-1 and insulin on HGP. In rats, we observed that intracerebroventricular (ICV) administration of IGF-1 or insulin markedly increased the glucose infusion rate (GIR) by >50% and suppressed HGP (P Likewise, ICV infusion of the InsR antagonist, S961, which also can bind HybridRs, interfered with the ability of central insulin, but not IGF-1 to increase the GIR. Furthermore, hyperinsulinemic clamps in mice lacking IGF-1Rs in AgRP neurons revealed ~30% reduction in the GIR in KO animals, which was explained by an impaired ability of peripheral insulin to completely suppress HGP (P
