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Morphologic and immunohistochemical analysis of the mouse intrinsic cardiac nervous system
Date Issued |
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2010-03-26 |
Purpose: To determine the morphologic and immunohistochemical patterns of the epicardiac ganglionated neural plexus (EGNP) on the whole-mounted (non-sectioned) mouse hearts. Methods: Quantitatively and qualitatively, the distribution of the cholinergic and adrenergic neural components was investigated using both the double and triple labeling of the general (protein gene product 9.5, PGP 9.5), cholinergic (choline acetyltransferase, ChAT) and adrenergic (tyrosine hydroxylase, TH) neuronal markers on whole-mount preparations of the mouse heart. Results: Intrinsic cardiac neurons were revealed only on the heart (atrial) base and they were mostly concentrated near the inferior vena cava on the right atrium and near the pulmonary veins on the left atrium. The ganglion number per one mouse heart was 19 ± 3. The approximate number of the epicardiac neurons was 1082 ± 160. Most neuronal somata expressed ChAT immunoreactivity (IR) suggesting that 83% neurons were cholinergic. We found that 3.5% neuronal somata expressed exceptionally TH-IR and 13.5% of the ganglionic cells are bi-phenotypic ones, i.e. they were IR for ChAT and TH. Strong staining for ChAT was observed in the axonal varicosities around the postganglionic ChAT-IR neurons. The plentiful ChAT-IR and TH-IR nerve fibers were identified within both the atrial and ventricular EGNP, but the predominance of TH-IR nerve fibers on the left dorsal and ventral atrial regions as well as the predominance of ChAT-IR fibers in the sinoatrial nodal region were evident. Conclusions: (1) In general, sympathetic and parasympathetic axons access the EGNP and distribute within it as the mixed nerve fibers, bundles and nerves; (2) there are symphatetic, parasympathetic and bi-phenotypic neurons in the mouse EGNP.