Aging and arterial hypertension are associated with alterations of cardiac autonomic nervous system

Abstract

BACKGROUND: Our previous work indicates that arterial hypertension affects intracardiac innervation of adult rats. Age-related changes are also known in the cardiac nervous system, e.g. the decrease of neuronal number. The next step of our research is to look at the influence of hypertension on ageing nerve structures: do the morphological alterations start with the young age already? How significant is the impact of this disease on older rats’ cardiac nerves? METHODS: Pilot study includes four groups: (i) young - 2 months old– (n=2) and (ii) old - 12 months old – (n=2) spontaneously hypertensive rats (SHR); (iii) young (n=2) and (iv) old (n=1) normotensive Wistar Kyoto rats’ (WKY). Whole-mount atrial and whole-mount ventricular preparations were made from rats hearts’. Neural structures were stained immunohistochemically for protein gene product 9,5 (PGP 9,5 – general neuronal marker). The number of positively stained nerves in the atrial left dorsal region and epicardial nerves of ventricles, located immediately below coronary sulcus, were calculated. Results were described as absolute numbers (n) or mean ± standard error, p≤0.05. RESULTS: The diameter of atrial nerves of young SHR (n=544) and WKY (n=571) were similar (29±1.3 vs 26±1.19 μm, p=0.082). The diameter of old SHR (n=763) and WKY (n=368) atrial nerves differed significantly (25±0.9 vs 31±1.8 μm, p=0.001). Regarding epicardial nerves, from young hearts’ ventricles, the amount (SHR n=308, WKY n=295) was similar, but the nerves’ diameter was different (24±1.1 vs 19±1 μm, p=0.02). When animals got older, the gap between the diameter became even bigger significantly: (SHR n=306, WKY n=208, 33±15 vs 24±1.5 μm, p<0.001). The changes during the time regarding nerve number is mixed: SHR 2 young rats with 308 nerves in total to 2 old rats with 306 nerves in total, WKY – young rats with 295 nerves in total to 1 old rat with 2[...].