Impact of Intranasal Insulin on Sympathetic Activity and Cerebral Vasodilation

Hypercapnic (5% carbon dioxide) air will be administered before and after intra-nasal insulin exposure.

Participants will be asked to repeatedly open and close their eyes. With eyes open, participants will focus on a visual image. This will be done before and after intra-nasal insulin exposure.

Participants will be administered human insulin (160 IU) as a bolus using an intra-nasal device.