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Selective sympathetic neural changes in hypertrophied right ventricle
The American Journal of Physiology
|August 11, 1982
Summary
Right ventricle pressure overload in guinea pigs reduced key enzyme activities, suggesting localized sympathetic nerve fiber loss. However, remaining nerves still responded to stress, indicating altered but not absent cardiac sympathetic regulation.
Area of Science:
- Cardiovascular Physiology
- Neurocardiology
Background:
- Right ventricular pressure overload is a significant stressor.
- Sympathetic nervous system plays a crucial role in cardiac function and adaptation.
- Understanding neural changes in cardiac hypertrophy is vital for managing heart conditions.
Purpose of the Study:
- To investigate the impact of sustained right ventricular pressure overload on cardiac sympathetic nerve activity in guinea pigs.
- To determine if changes in sympathetic activity are localized to the right ventricle or systemic.
- To assess the functional response of remaining sympathetic nerves in hypertrophied cardiac tissue.
Main Methods:
- Induction of selective pressure overload on the right ventricle in guinea pigs via pulmonary artery constriction.
- Measurement of tyrosine hydroxylase and dopamine-beta-hydroxylase activities in various cardiac regions and neural tissues.
- Assessment of norepinephrine turnover and response to cold-induced sympathetic activation.
Main Results:
- Early and sustained reductions in tyrosine hydroxylase and dopamine-beta-hydroxylase activities were observed specifically in the right ventricle.
- No significant changes in tyrosine hydroxylase activity were found in the sinoatrial nodal region, atrioventricular nodal region, or the left ventricle.
- Reductions in right ventricular enzyme activity were consistent across varying durations of constriction, hypertrophy levels, and hepatic congestion.
- Despite reduced enzyme activity, remaining sympathetic nerves in the hypertrophied right ventricle responded normally to cold-induced sympathetic activation.
Conclusions:
- Selective pressure overload leads to localized decreases in sympathetic nerve activity within the right ventricle.
- These changes are likely linked to the process of pressure-overload-induced cardiac hypertrophy.
- Cardiac sympathetic neural regulation is altered, not abolished, in hypertrophied right ventricular tissue.