TABLE 1

Summary of experimental conditions

Studies protocolsn
1: Clamps
    Euglycemic clamps
aCSF (icv)7
Ex4 (icv)6
    Hyperglycemic clamps
aCSF (icv)7
aCSF (icv) (GLP-1R KO)6
Ex4 (icv)7
Ex9 (icv)5
Ex4 + hydrogen peroxide (20 nmol/min) (icv)5
2: Saline intravenous infusion
        aCSF (icv)6
3: Basal blood flow and heart rate studies
aCSF (icv)7
Ex4 (icv)12
Ex9 (icv)8
PBS (icv)4
Hydrogen peroxide (2 nmol/min, icv)4
Hydrogen peroxide (20 nmol/min, icv)5
4: Vagal activity studies
aCSF (icv)5
Ex4 (icv)4
5: ROS studies
aCSF (icv, saline iv, WT)5
aCSF (icv, clamp 5.5 mmol/l, WT)15
aCSF (icv, clamp 20 mmol/l, WT)10
Ex4 (icv, clamp 5.5 mmol/l, WT)8
Ex4 (icv, clamp 20 mmol/l, WT)14
aCSF (icv, clamp 5.5 mmol/l, GLP-1R KO)5
aCSF (icv, clamp 20 mmol/l, GLP-1R KO)5
6: NOS activity studies
aCSF (icv, clamp 20 mmol/l)5
Ex4 (icv, clamp 20 mmol/l)5
  • The number of mice studied (n) is indicated for each experimental condition. aCSF, mice infused with artificial cerebrospinal fluid into the brain (intracerebroventricular [icv]). Some mice were clamped with insulin in euglycemic or hyperglycemic conditions or underwent a saline infusion equivalent to the corresponding insulin and glucose infusion volumes and rates performed during the clamp conditions. Some mice were studied in basal conditions (no insulin, glucose, or saline infusion) only. Hydrogen peroxide was used at the concentration of 2 or 20 nmol/min icv only, as specified. The vagal activity was recorded in response to aCSF or Ex4 icv infusions in a subset of mice. ROS production was assessed in all conditions in WT or GLP-1 receptor knockout mice (GLP-1R KO) mice. The activity of the NOS was studied in a subset of mice during hyperglycemic-hyperinsulinemic clamp conditions in the presence or absence of Ex4 icv.