Social isolation induced a significant increase in resting heart rate and
reduction in heart rate variability. Dysfunction of the intrinsic cardiac
nervous system is implicated in the genesis of cardiovascular diseases.
Previous evidence suggests that cardiac ganglia contain noradrenergic
neurons. Thus, immunohistochemical expression of catecholaminesynthesizing
enzyme tyrosine hydroxylase (TH) and vesicular monoamine transporter 2
(VMAT2) were analyzed, as well as the effects of social isolation stress on
mRNA and protein levels of this enzyme and transporter in the intrinsic
cardiac nervous system of adult rats. Our results indicate that cardiac
ganglion neurons express TH and VMAT2 immunoreactivity. Chronic isolated
stress of rats caused a decrease in TH mRNA and VMAT2 mRNA in the neurons of
intrinsic cardiac ganglia. No significant alterations in the protein levels
of TH and VMAT2 were observed in these neurons. These data indicate that the
neurons of intrinsic cardiac ganglia express TH as well as VMAT2 but that
social isolation stress does not change their protein levels.