Muscarinic and beta-adrenergic regulation of heart rate, force of contraction and calcium current is preserved in mice lacking endothelial nitric oxide synthase
Summary
This summary is machine-generated.Nitric oxide synthase 3 (NOS3) is not essential for the autonomic control of cardiac function. Studies in NOS3-knockout mice show normal heart responses to beta-adrenergic and muscarinic agonists.
Area Of Science
- Cardiovascular Physiology
- Autonomic Nervous System
- Molecular Cardiology
Background
- Nitric oxide (NO), produced by NO synthase (NOS), is a key signaling molecule in the vasculature, mediating parasympathetic vasodilation.
- NOS3, specifically, is expressed in cardiac myocytes, and its inhibition affects cardiac function, suggesting a role in autonomic heart control.
- Previous studies indicated that NOS and guanylyl cyclase inhibitors antagonize muscarinic agonist effects on heart rate, contractility, and ion currents.
Purpose Of The Study
- To investigate the role of NOS3 in the autonomic regulation of cardiac function.
- To determine if NOS3 deficiency impacts the heart's response to autonomic stimulation.
- To examine the necessity of NOS3 for normal cardiac autonomic control.
Main Methods
- Utilized genetically engineered mice deficient in NOS3 (NOS3-knockout).
- Assessed chronotropic and inotropic responses in isolated cardiac tissue preparations from NOS3-knockout and wild-type mice.
- Examined beta-adrenergic and muscarinic stimulation/inhibition effects on calcium currents in cardiac myocytes.
- Performed RT-PCR to check for upregulation of other NOS isoforms and assessed Gi/Go proteins and muscarinic receptor density.
Main Results
- Chronotropic and inotropic responses to beta-adrenergic and muscarinic agonists were unaltered in NOS3-knockout mice.
- Cardiac myocyte responses to beta-adrenergic stimulation and muscarinic inhibition of calcium currents were similar between NOS3-knockout and wild-type mice.
- NOS3-knockout mice exhibited defective parasympathetic regulation of vascular tone, but not cardiac function.
- No upregulation of other NOS isoforms or alterations in Gi/Go proteins and muscarinic receptor density were observed.
Conclusions
- NOS3 is not obligatory for the normal autonomic control of cardiac muscle function.
- The findings refute the hypothesis that NOS3 is essential for mediating autonomic effects on the heart.
- While NOS3 plays a role in vascular tone regulation, its absence does not impair cardiac autonomic control mechanisms.
View abstract on PubMed