Adenosine increases sympathetic nerve traffic in humans.

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Autonomic Nervous System

Background:

• Adenosine is a hypotensive agent in animals and anesthetized patients, with minimal reflex sympathetic activation.
• In conscious subjects, adenosine paradoxically increases systolic blood pressure and heart rate.
• The mechanism behind this discrepancy requires investigation.

Purpose of the Study:

• To investigate the cardiovascular and respiratory effects of adenosine in conscious humans.
• To determine if adenosine-induced increases in blood pressure and heart rate are linked to sympathetic activation.
• To directly measure muscle sympathetic nerve traffic during adenosine administration.

Main Methods:

• Direct recordings of muscle sympathetic nerve traffic from the peroneal nerve in normal subjects.
• Intravenous administration of adenosine at 80 micrograms/kg/min.
• Measurement of heart rate, systolic blood pressure, diastolic blood pressure, and minute ventilation.

Main Results:

• Adenosine increased heart rate, systolic blood pressure, and minute ventilation.
• A dose-dependent increase in muscle sympathetic nerve activity was observed.
• Adenosine caused a greater sympathetic response than nitroprusside for equivalent diastolic blood pressure reduction, indicating baroreceptor unloading is not the sole cause.

Conclusions:

• Adenosine increases sympathetic tone in conscious individuals, likely by activating afferent nerves, including arterial chemoreceptors.
• This sympathetic activation by adenosine may be more prevalent than previously understood.
• Adenosine's effects on afferent nerves contrast with its inhibitory actions on efferent systems.