VMH GLT-1 knockdown studies. A: GLT-1 protein levels in the VMH of control (n = 7), RH (n = 7), and RH animals that received the GLT-1 small interfering RNA (RH + GLT-1 siRNA) (n = 6) standardized to β-actin. B: Extracellular glutamate concentrations in the VMH of control, RH, and RH + GLT-1 siRNA under baseline (white bars) and hypoglycemic clamp (black bars) conditions. C and D: Peak plasma glucagon and epinephrine concentrations of control, RH, and RH + GLT-1 siRNA during the hypoglycemic clamp. Further reducing GLT-1 protein levels in the VMH of RH animals increased VMH extracellular glutamate and improved the counterregulatory hormone responses to hypoglycemia. Data are mean ± SEM. *P < 0.05 vs. control; ¶P < 0.05 vs. control. R.O.D., relative optical density.