Figure 2. Nerve growth factor mainly concentrates in the cardiomyocyte submembrane portion contacted by sympathetic neurons in human hearts.

A , confocal immunofluorescence (IF) analysis of human heart sections, co‐stained with antibodies against SNAP25 (top panel) and nerve growth factor (NGF) (middle panel). The bottom panel shows the bright field image. B, magnification of the white box in (A), showing the merged fluorescence and bright field images. SN, sympathetic neuron; CM, cardiomyocyte. Arrows indicate NGF puncta in the neuronal process. C, quantification of the fluorescence intensity of SNAP25 (red signal) and NGF (green signal) in correspondence with the neuronal varicosity (2) or the inter‐varicosity space (1). Bars represent SD (n = 15 neuro‐cardiac contacts from two different human hearts). [Colour figure can be viewed at wileyonlinelibrary.com]