Catecholaminergic and peptidergic nerve components of intramural ganglia in the rat heart

Abstract

Immunohistochemical properties of the terminal nerve network in the rat heart were assessed by use of the elution-restaining method. The colocalization of the enzymes involved in catecholamine synthesis (tyrosine hydroxylase--TH. dopamine-beta-hydroxylase--DBH) as well as the respective distributions of the neuropeptides associated with the adrenergic nervous system (neuropeptide tyrosine--NPY, C-terminal flanking peptide of neuropeptide Y--C-PON) were studied in series of serial sections throughout the interatrial septum and the atrioventricular junction. Our data suggest that ganglion cells of sulcus terminalis as well as the epicardial ganglia enclosed between the superior vena cava and ascending aorta are VIP- and TH-negative, but neuropeptide Y- and DBH-immunoreactive. They give rise to three intraseptal nerves directed towards the specialised structures of the atrioventricular junction. These nerve fascicles contain abundant, thick TH-immunoreactive nerve fibres and scarce, thin NPY- and DBH-immunoreactive fibres. The cell bodies of the intramural ganglion cells localized between the right and left branches of the bundle of His (Moravec and Moravec 1984) are strongly TH- and DBH-immunoreactive. They are innervated by thick nerve fibres having the same immunohistochemical properties (NPY- and DBH-immunoreactivities) as those of a subpopulation of the epicardial ganglion cells and seem to supply some of the TH-immunoreactive nerve fibres directed via the intraseptal nerves to the epicardial ganglia. The existence of a multicomponent nerve network, characterized by a reciprocal innervation of the sinus node and atrioventricular node areas, is suggested by our immunohistochemical data.

Monoamine- and Histamine-Synthesizing Enzymes and Neurotransmitters Within Neurons of Adult Human Cardiac Ganglia

“…For example, dopamine ␤-hydroxylase but not tyrosine hydroxylase immunoreactivity is found within rat cardiac ganglia near the sinoatrial node, 4 whereas dopamine ␤-hydroxylase and tyrosine hydroxylase immunoreactivity are found in ganglia near the atrioventricular node of guinea pigs. 5 Tyrosine hydroxylase-immunoreactive nerve fibers projecting through cardiac ganglia and varicosities adjacent to neurons also occur.…”

“…For example, early studies using histofluorescence techniques do not report catecholamines within neurons of rat or guinea pig cardiac ganglia. 18 Recently, however, key marker enzymes in catecholaminergic neurons, including tyrosine hydroxylase and dopamine ␤-hydroxylase, were found in rat 3,4 and guinea pig 1,5 cardiac ganglia. To the best of our knowledge, no studies examining the presence of phenylethanolamine-N-methyltransferase (PNMT, which synthesizes epinephrine), tryptophan hydroxylase (which synthesizes serotonin), and histidine decarboxylase (which synthesizes histamine) within cardiac ganglia exist in the literature.…”

“…Recent evidence, however, suggests that cardiac ganglia contain a heterogeneous population of neurons capable of synthesizing or responding to several different neurotransmitters and neuropeptides. Enzymes involved in the synthesis of nitric oxide, 1,2 dopamine, 3,4 and norepinephrine [3][4][5] exist within nonhuman mammalian cardiac ganglia. Vasoactive intestinal peptide, 1,2,6 substance P, 1,2 somatostatin, 1,2 and neuropeptide Y [1][2][3][4]7 immunoreactivity also exists within cardiac ganglia.…”

“…Enzymes involved in the synthesis of nitric oxide, 1,2 dopamine, 3,4 and norepinephrine [3][4][5] exist within nonhuman mammalian cardiac ganglia. Vasoactive intestinal peptide, 1,2,6 substance P, 1,2 somatostatin, 1,2 and neuropeptide Y [1][2][3][4]7 immunoreactivity also exists within cardiac ganglia. Receptor characterization studies suggest not only cholinergic but also ␤-adrenergic, 1,8,9 serotonergic, 10 and purinergic 1,11,12 receptors on ganglionic neurons.…”

Autonomic cardiac nerves: literature review

“…Moravec et al [43] found that ganglionic cells in epicardial ganglia and around the terminal groove (sulcus terminalis) are negative to VIP and TH and immunopositive to NPY and DBH. On the other hand, the bodies of intramural ganglia located between the right and the left branch of the His bundle are highly immunoreactive to TH and DBH.…”