Regional distribution and extrinsic innervation of intrinsic cardiac neurons in the guinea pig

Abstract

Mammalian intrinsic cardiac neurons subserve different functions in different cardiac regions, but the regional anatomical organisation of the intracardiac nervous system is not well understood. We investigated the quantitative and qualitative distribution of cholinergic and adrenergic elements, and the intracardiac pathways of extrinsic cardiac nerves, in whole‐mount preparations of guinea pig atria. Protein gene product 9.5 immunoreactivity (PGP 9.5‐IR) marked intracardiac neuronal elements; immunoreactions for choline acetyltransferase (ChAT‐IR) and tyrosine hydroxylase (TH‐IR) distinguished cholinergic and adrenergic components, respectively. Catecholamine‐containing components were identified by aldehyde‐induced fluorescence histochemistry. Mean total number of atrial neurons was 1510 ± 251 (SE); 85% of these occurred in ganglia of ≤ 20 neurons. All neuronal somata expressing PGP 9.5‐IR also expressed ChAT‐IR, suggesting that these neurons were cholinergic. Right (RA) and left (LA) atria had statistically similar neuronal densities (6.4 ± 1.2 and 2.4 ± 0.7 neurons/mm2, respectively; analysis of variance, P≤0.05). Neurons in RA were concentrated intercavally; LA neurons were concentrated near pulmonary vein ostia. Greatest density occurred in the interatrial septum (16.3 ± 4.0 neurons/mm2). No neuronal somata expressed TH‐IR or contained detectable amines but these elements were expressed by somata of small cells (mean total 124 ± 33) throughout the atria, primarily associated with ganglia. Amine‐ and TH‐ containing varicosities were also present in ganglia, representing potential sites for adrenergic modulation of ganglionic neurotransmission. Branches of extrinsic cardiopulmonary and vagus nerves were distributed to all parts of both atria. The organisation of the intracardiac nervous system revealed in this study will facilitate further investigations of regional autonomic control of the heart. J. Comp. Neurol. 407:303–317, 1999. © 1999 Wiley‐Liss, Inc.

Immunohistochemical analysis of intracardiac ganglia of the rat heart

“…Previous studies in the rat have estimated the total number of intracardiac neurons above the atrioventricular groove at 4,000, organised into four major groups (Pardini et al 1987). These observations contrast greatly with findings in other small mammals such as guinea pigs, which have an estimated 1,500 neurons, the majority of which are organised into ganglia containing fewer than 20 cells (Leger et al 1999). Thus even within small mammals, there is a great deal of diversity in the gross anatomy of No intracardiac neurons were immunoreactive to TH (A, A', z-series stacks).…”

Presence and co-localization of vasoactive intestinal polypeptide with neuronal nitric oxide synthase in cells and nerve fibers within guinea pig intrinsic cardiac ganglia and cardiac tissue

“…The pH was maintained at 7.4 by aeration with 95% O 2 , 5% CO 2 . The guinea pig possesses two areas of atrial tissue particularly rich in cardiac ganglia: an area around the superior vena cava and an area surrounding the coronary sinus, interatrial septum, and small cardiac vein (Mawe et al 1996;Kennedy et al 1998;Horackova et al 1999;Leger et al 1999;Calupca et al 2000a,b). In the present study of the VIP innervation of the intrinsic cardiac ganglia, an atrial whole-mount preparation including the region around the superior vena cava, the coronary sinus, and small cardiac vein was prepared.…”

Expression and Distribution of Dopamine Transporter in Cardiac Tissues of the Guinea Pig

“…Different reports have been demonstrated inmunorreactivity for cholinergic, noradrenergic, histaminergic, nitrergic, peptidergic, and serotonergic neurotransmitters in cardiac tissues [15,19,20,24,[27][28][29]. Also it has been reported, different distributions of immunoreactivity for tyrosine hidroxilase and dopamine beta hydroxilase a specific markers for adrenergic neurons in mammal hearts [30,31].…”

“…The tubes were inverted during 2 h at 4°C, and centrifuged at 45,000g (18,500 rpm) for 20 min at 4°C. The supernatants were kept for protein assay and Western blot [19]. Protein content was determined according to Bradford's method using a Bio-Rad kit.…”

“…The mammal heart is an organ with a complex intrinsic nervous system that is organized in ganglion and extents network of nerve fibers [15][16][17][18][19][20][21]. Numerous studies have demonstrated the presence of different components of cholinergic and sympathetic neurotransmission markers as choline and noradrenaline transporters that support the presence of cholinergic and sympathetic nerve cells into the heart [22][23][24][25][26].…”