The contribution of the sympathetic innervation to the postnatal
development of cardiac contractility remains unclear. In this
study, the postnatal maturation of cardiac contractility was
compared in control rats and rats after chemical sympathectomy.
The chemical sympathectomy was induced by administration of
6-hydroxydopamine to newborn rats. At days 20, 40 and 60 of
postnatal life, the contractile parameters and concentrations of
sympathetic neurotransmitters were measured in both right and
left ventricles. In rats with chemical sympathectomy,
concentrations of norepinephrine were reduced almost
completely in both ventricles at all time points. The contractility
of the left ventricle papillary muscles was substantially decreased
at all time points. In contrast, the contractility of the right
ventricle papillary muscles was decreased only transiently,
showing a recovery at day 60 regardless of the permanently
decreased concentration of norepinephrine. The concentration of
neuropeptide Y, another neurotransmitter present in sympathetic
nerves, showed the same developmental trend as contractility:
permanent reduction in the left ventricle, transient reduction with
a recovery at day 60 in the right ventricle. The data indicate that
the sympathetic nervous system plays an important role in the
postnatal development of cardiac contractility and neuropeptide Y
may contribute to this effect.
The Effects of T-588, a Novel Cognitive Enhancer, on Noradrenaline Uptake and Release in Rat Cerebral Cortical Slices
