Adrenergic supersensitivity and impaired neural control of cardiac electrophysiology following regional cardiac sympathetic nerve loss

Figures

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  Figure 1. Effects of regional toxin application on sympathetic nerve fiber density. (A,B) Whole-heart labeling of tyrosine hydroxylase (TH) demonstrates fewer visible sympathetic nerve fibers on the anterior surface (where toxin solution is applied) of the DBH-Sap heart (B) compared to control (A). (C,D) The posterior surface is similar between control and DBH-Sap groups. (E,F) Short axis TH images of the anterior (E) and posterior (F) surface of a DBH-Sap mouse heart. (G,H) Sympathetic nerve fiber density from anterior base (G) and apex (H) regions 5 days after treatment. At the apex, the percent TH + area was significantly reduced in the epicardium of the DBH-Sap group, and there was also a main effect between groups (***p < 0.001, main effect control vs. DBH-Sap, two-way ANOVA, H). Data are mean ± SD; analyzed with GraphPad Prism 8.3 (GraphPad Software, San Diego, CA, USA); control: n = 3; DBH-Sap: n = 3; **p < 0.01, ***p < 0.001.

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  Figure 2. Masson’s trichrome staining of short-axis sections. (A) Cross-sectional staining of a control heart and 20 × images of the epicardial/sub-epicardial regions from anterior and posterior surfaces of the heart. (B) Cross-sectional staining of a DBH-Sap (toxin-exposed) heart and 20 × images of the epicardial/sub-epicardial regions from anterior and posterior surfaces. No overt myocardial damage was observed in any heart from either group.

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  Figure 3. Impact of isoproterenol (ISO) stimulation on action potential duration (APD80) and APD dispersion at a pacing cycle length of 100 ms. (A,B) Example maps of APD80 at baseline (BL) and with ISO in both groups. (C,D) Example maps and optical AP signals showing the difference in APD (ΔAPD80) from BL with ISO stimulation. (E) Mean APD80 at BL and with ISO from base and apex regions of both groups. (F) Mean APD dispersion at BL and with ISO in both groups. Data are mean ± SD; analyzed with GraphPad Prism 8.3 (GraphPad Software, San Diego, CA, USA); control: n = 4; DBH-Sap: n = 6; **p < 0.01.

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  Figure 4. Calcium transient duration (CaTD80) and tau in control and DBH-Sap hearts at baseline (BL) and with isoproterenol (ISO) stimulation at a pacing cycle length of 100 ms. (A,B) Example maps of CaTD80 at BL and with ISO in both groups. (C,D) Example maps and optical Ca2+ signals showing the difference in CaTD (ΔCaTD80) from BL with ISO stimulation. (E) Mean CaTD80 at BL and with ISO from base and apex regions of both groups. (F) Mean tau at BL and with ISO for both groups. Data are mean ± SD; analyzed with GraphPad Prism 8.3 (GraphPad Software, San Diego, CA, USA); control: n = 6; DBH-Sap: n = 8; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

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  Figure 5. (A) Example optical Ca2+ signals showing diastolic Ca2+ elevation primarily at the apex but not at the base of a DBH-Sap heart following cessation of rapid pacing (70 ms pacing cycle length, PCL). (B) Example optical map of relative diastolic Ca2+ elevation in a DBH-Sap heart immediately after cessation of pacing at a PCL of 70 ms. (C,D) Mean diastolic Ca2+ elevation at BL (C) and with ISO (D) from the base and apex regions of both group after a 70 ms pacing train. (E) Amplitude of recovery of Ca2+ release at the base with progressively shorter S2 coupling intervals. (F) Amplitude of recovery of Ca2+ release at the apex with progressively shorter S2 coupling intervals. There was a main effect of animal group (p < 0.0001 control vs. DBH-Sap) and differences at S2 = 60, 70, and 80 ms as indicated. (G) CaT alternans magnitude (L large; S small) between control and DBH-Sap hearts at the base. There was a main effect of animal group (p = 0.0002 control vs. DBH-Sap) and a difference at PCL = 60 ms as indicated. (H) CaT alternans magnitude at the apex. There was no main effect of animal group, but alternans magnitude was different at PCL = 60 ms. Data in (E–H) were analyzed by a two-way…

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  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.