Summary BACKGROUND The intrinsic neural plexus of the mouse heart has not been adequately investigated despite the extensive use of this species in experimental cardiology. OBJECTIVE We determined the distribution of cholinergic, adrenergic and sensory neural components in whole-mount mouse heart preparations using double immunohistochemical labeling. METHODS AND RESULTS Intrinsic neurons were concentrated within 19±3 ganglia (n = 20 mice) of varying size, scattered on the medial side of the inferior caval (caudal) vein on the right atrium and close to the pulmonary veins on the left atrium. Of a total of 1082±160 neurons, most somata (83%) were choline acetyltransferase (ChAT)-immunoreactive, while 4% were tyrosine hydroxylase (TH)-immunoreactive; 14% of ganglionic cells were biphenotypic for ChAT and TH. The most intense ChAT staining was observed in axonal varicosities. ChAT was evident in nerve fibers interconnecting intrinsic ganglia. Both ChAT and TH immunoreactivity were abundant within the nerves accessing the heart. However, epicardial TH-immunoreactive nerve fibers were predominant on the dorsal and ventral left atrium, whereas most ChAT-positive axons proceeded on the heart base toward the large intrinsic ganglia and on the epicardium of the root of the right cranial vein. Substance P-positive and calcitonin gene-related peptide-immunoreactive nerve fibers were abundant on the epicardium and within ganglia adjacent to the heart hilum. Small intensely fluorescent cells were grouped into clusters of 3–8 and dispersed within large ganglia or separately on the atrial and ventricular walls. CONCLUSIONS While some nerves and neuronal bundles of the mouse epicardial plexus are mixed, most express either adrenergic or cholinergic markers. Therefore, selective stimulation and/or ablation of the functionally distinct intrinsic neural pathways should allow the study of specific effects on cardiac function.

Tunneling nanotubes and epithelial bridges are recently discovered new forms of intercellular communication between remote cells allowing their electrical synchronization, transfer of second messengers and even membrane vesicles and organelles. In the present study, we demonstrate for the first time in primary cell cultures prepared from human laryngeal squamous cell carcinoma (LSCC) samples that these cells communicate with each other over long distances (up to 1 mm) through membranous tunneling tubes (TTs), which can be open-ended or contain functional gap junctions formed of connexin 43. We found two types of TTs, containing F-actin alone or F-actin and α-tubulin. In the LSCC cell culture, we identified 5 modes of TT formation and performed quantitative assessment of their electrical properties and permeability to fluorescent dyes of different molecular weight and charge. We show that TTs, containing F-actin and α-tubulin, transport mitochondria and accommodate small DAPI-positive vesicles suggesting possible transfer of genetic material through TTs. We confirmed this possibility by demonstrating that even TTs, containing gap junctions, were capable of transmitting double-stranded small interfering RNA. To support the idea that the phenomenon of TTs is not only typical of cell cultures, we have examined microsections of samples obtained from human LSCC tissues and identified intercellular structures similar to those found in the primary LSCC cell culture.

Summary BACKGROUND Both normal and genetically modified mice are excellent models to investigate molecular mechanisms of arrhythmogenic cardiac diseases that may associate with an imbalance between the sympathetic and the parasympathetic nervous input to the heart. OBJECTIVE We sought to: (1) determine the structural organization of the mouse cardiac neural plexus; (2) identify extrinsic neural sources and their relationship with the cardiac plexus; and (3) reveal any anatomical differences in the cardiac plexus between mouse and other species. METHODS Cardiac nerve structures were visualized employing histochemical staining for acetylcholinesterase (AChE) on whole heart and thorax-dissected preparations derived from 25 mice. To confirm reliability of staining parasympathetic and sympathetic neural components in the mouse heart we applied a histochemical method for AChE and imunohistochemistry for tyrosine hydroxylase (TH) and/or choline acetyltransferase (ChAT) on whole mounts preparations from 6 mice. RESULTS The double immunohistochemical labeling of TH and ChAT on AChE positive neural elements in mouse whole mounts demonstrated equal staining of nerves and ganglia for AChE that were positive for both TH and ChAT. The extrinsic cardiac nerves access the mouse heart at the right (RCV) and left (LCV) cranial veins and interblend within the ganglionated nerve plexus of the heart hilum that is persistently localized on the heart base. Nerves and bundles of nerve fibers extend epicardially from this plexus to atria and ventricles by left dorsal, dorsal right atrial, right ventral, and ventral left atrial routes or subplexuses. The RCV received extrinsic nerves mainly originated from the right cervicothoracic ganglion and a branch of the right vagus nerve, while the LCV was supplied by extrinsic nerves from the left cervicothoracic ganglion and the left vagus nerve. The majority of intrinsic cardiac ganglia were localized on the heart base at the roots of pulmonary veins. These ganglia were interlinked by interganglionic nerves into the above mentioned nerve plexus of the heart hilum. In general, the examined hearts contained 19 ± 3 ganglia, which gave a cumulative ganglion area of 0.4 ± 0.1 mm2. CONCLUSION Despite substantial anatomical differences in ganglion number and distribution, the structural organization of the intrinsic ganglionated plexus in the mouse heart corresponds in general to other mammalian species, including human.

SummaryBACKGROUND-The sheep is routinely used in experimental cardiac electrophysiology and surgery.

No abstract