Fig. 1
Spleen voltammetry signal responsive to changes in NE. a Carbon fiber working electrode and a reference electrode are inserted in the spleen for recording fast scan cyclic voltammetry. A bipolar electrode is placed on the splenic neurovascular bundle for splenic nerve stimulation; in other experiments, the stimulating electrode is placed on the cervical vagus nerve or the splanchnic nerve. b Averaged cyclic voltammograms during voltage sweeps (− 0.4 V to 1.3 V and back to − 0.4 V) in vitro (in heparinized blood, 0 and 3.3 µg/mL NE) and in vivo (in live spleen, 0.5 µg/mL est. peak blood NE concentration); the vertical dotted line denotes the NE oxidation voltage (Eo), and the calculation of oxidation current (io) is represented. c Representative time-resolved voltammograms during intravenous bolus injection of NE (100 μL). Top panels: current amplitude (represented by color) at different values of sweeping voltage (ordinate), at different times relative to NE injection (abscissa). Outer black box represents the voltage and time boundaries of the peak oxidation current signal (outer boundaries); horizontal line inside box marks the oxidation potential for NE. Dashed vertical line denotes time of drug administration. Bottom panels: time-course of oxidation current, calculated as shown in b, during the same time period. Grey-shaded area under the io trace represents the total oxidation charge (Qo) generated within the time boundaries indicated in the top panels. d Qo at multiple NE concentrations measured in 3 animals, at different estimated NE concentrations. Solid line represents linear fit; Pearson’s r = 0.79, p = 0.01