Clinical measurements included whole-body norepinephrine kinetics [ spillover rate , plasma clearance , and the steady state ratio of tritiated 3,4-dihydroxyphenylglycol to tritiated norepinephrine ( [ ( 3 ) H ] - DHPG to [ ( 3 ) H ] - NE ) as an index of neuronal uptake-1 ] , muscle sympathetic nerve activity , spontaneous baroreflex sensitivity , euglycemic hyperinsulinemic clamp , oral glucose tolerance test , ambulatory blood pressure , and Doppler echocardiography .