Paraventricular Nucleus Modulates Excitatory Cardiovascular Reflexes during Electroacupuncture

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Integrative Medicine

Background:

• The paraventricular nucleus (PVN) is crucial for regulating sympathetic outflow and blood pressure.
• Somatic afferent stimulation activates hypothalamic PVN neurons, which project to sympathoexcitatory cardiovascular regions like the rostral ventrolateral medulla (rVLM).
• Electroacupuncture (EA) applied to the median nerve (P5-P6) can modulate sympathoexcitatory cardiovascular responses.

Purpose of the Study:

• To investigate the role of the PVN and its projections to the rVLM in mediating the blood pressure-lowering effects of EA.
• To elucidate the underlying neural and opioid mechanisms involved in EA's cardiovascular modulation.

Main Methods:

• Anesthetized cats underwent monitoring of heart rate and mean blood pressure.
• Bradykinin was applied to the gallbladder to induce pressor reflex responses.
• Bilateral EA stimulation at P5-P6 acupoints was performed, followed by PVN inhibition with naloxone and opioid receptor blockade.

Main Results:

• EA stimulation significantly reduced bradykinin-induced pressor responses.
• Inhibition of the PVN with naloxone reversed the inhibitory effect of EA.
• EA reduced the activity of cardiovascular barosensitive rVLM and PVN neurons projecting to the rVLM, an effect reversed by opioid receptor blockade.

Conclusions:

• The PVN and its projections to the rVLM are integral to acupuncture's modulation of elevated blood pressure.
• EA exerts its blood pressure-lowering effects through a PVN opioid mechanism, influencing sympathoexcitatory pathways.