Immunohistochemical evidence of nNOS containing fibres in the cardiac ventricle of the rabbit (1169.4)

Abstract

Vagal stimulation (VS) is a popular novel therapy in heart failure where its potential in ventricular arrhythmia prophylaxis is highlighted by animal studies showing that VS protects against ventricular fibrillation through nitric oxide (NO). This implies that there are vagal nerves containing neuronal nitric oxide synthase (nNOS) in the ventricle but, anatomical evidence is absent. Our aim was to characterise the phenotype of intrinsic cardiac nerves in the rabbit using immunohistochemistry for tyrosine hydroxylase (TH), choline acetyltransferase (ChAT) and nNOS (n=6). In the atrial and ventricular walls (Figure), TH, ChAT and nNOS positive nerve fibers and cell bodies exist. ChAT and nNOS positive structures predominate in the atria in large and small ganglia. nNOS positive somata and nerve fibers were present within ventricular epi‐ and endo‐cardial nerves, along Purkinje fibers and within the myocardium. The distribution of TH, ChAT and nNOS nerve fibers within epicardial nerve bundles on the anterior (A) and posterior (P) aspects of the left ventricle varied. TH fibres predominate over ChAT and nNOS (TH ‐ 64% (A) 68% (P); ChAT ‐ 10% (A) 8% (P); nNOS ‐ 10% (A) 10% (P)). In summary, we show the first direct evidence of nitrergic nerves within the rabbit intrinisc cardiac nervous system, in particular within the cardiac ventricle, implicating the key role that nitric oxide plays in neurocardiac control.$graphic_71E67ABC‐E99E‐4E1E‐BE16‐51627FC397DE$Grant Funding Source: Supported by Research Council of Lithuania and the British Heart Foundation