Sympathetic modulation of endothelium-derived relaxing factor

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Endothelial Function

Background:

• Endothelium-derived relaxing factor (EDRF) plays a crucial role in regulating vascular tone.
• The potential involvement of the sympathetic nervous system in mediating the effects of EDRF inhibition on blood pressure requires investigation.

Purpose of the Study:

• To investigate whether the sympathetic nervous system mediates the release of endothelium-derived relaxing factor (EDRF).
• To determine the role of the autonomic nervous system in the pressor response following EDRF inhibition.

Main Methods:

• Anesthetized rats were subjected to beta-blockade (propranolol), ganglionic blockade (hexamethonium), or mechanical pithing.
• Endothelium-derived relaxing factor (EDRF) was inhibited using NG-monomethyl-L-arginine (L-NMMA) or N omega-nitro-L-arginine-methyl ester (L-NAME).
• Blood pressure responses were measured under various conditions, including restoration of normotensive levels with vasoconstrictors.

Main Results:

• Inhibition of EDRF (L-NMMA or L-NAME) caused a significant increase in blood pressure in control rats.
• Neither beta-blockade nor ganglionic blockade altered the pressor response to EDRF inhibition.
• Mechanical pithing did not affect the pressor response to L-NAME, even when blood pressure was restored with vasoconstrictors.

Conclusions:

• The pressor response to EDRF inhibition is independent of an intact autonomic nervous system.
• The baroreceptor reflex buffering and absence of EDRF may contribute to enhanced pressor responses in specific experimental conditions.