Figure 6.

Electrophysiological responses to sympathetic nerve stimulation (SNS) during sinus rhythm and with pacing. (A) Photograph of the mouse innervated heart preparation. (B) Heart rate in control and DBH-Sap groups at baseline (BL) and with SNS. (C) Example difference maps (ΔAPD₈₀) demonstrating APD prolongation with SNS compared to BL. (D) Mean APD₈₀ from base and apex regions at BL and with SNS in both groups. (E) Example difference maps (ΔCaTD₈₀) demonstrating CaTD shortening with SNS compared to BL. (F) Mean CaTD₈₀ from base and apex regions at BL and with SNS in both groups. For panels (B–F) hearts are in sinus rhythm with and without SNS. (G) Time constant of Ca²⁺ decay (tau) of the whole heart at BL and with SNS in both groups at a pacing cycle length of 100 ms. (H) Mean diastolic Ca²⁺ elevation at base and apex regions of both groups following a 70 ms pacing train with SNS. Data are mean ± SD; analyzed with GraphPad Prism 8.3 (GraphPad Software, San Diego, CA, USA); control: n = 3–4; DBH-Sap: n = 6; *p < 0.05, **p < 0.01, ***p < 0.001.