Adenosine A_2A receptors in the rostral ventrolateral medulla participate in blood pressure decrease with...

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Complementary Medicine

Background:

• Acupuncture is a widely used complementary therapy for managing high blood pressure (BP).
• The precise mechanisms by which acupuncture lowers BP, particularly in sustained hypertension, are not fully understood.
• Previous research suggests a role for adenosine A_2A receptors (A_2AR) in the rostral ventrolateral medulla (rVLM) in electroacupuncture's (EA) acute BP-lowering effects.

Purpose of the Study:

• To investigate whether the activation of A_2AR in the rVLM contributes to the sustained BP-lowering effects of a course of EA treatment in hypertensive rats.
• To determine if a four-week EA regimen modulates A_2AR expression or function in the rVLM of salt-sensitive hypertensive rats.

Main Methods:

• Dahl salt-sensitive hypertensive rats (DSHRs) underwent a four-week treatment protocol of EA (twice weekly) or sham-EA.
• The effect of EA on BP was assessed, and subsequently, the role of rVLM A_2AR was examined using an A_2AR antagonist (SCH 58261) and agonist (CGS-21680) via microinjection.
• A_2AR levels in the rVLM were quantified using Western blot analysis after the treatment period.

Main Results:

• EA treatment significantly reduced BP in DSHRs, an effect not observed with sham-EA or no needling.
• The BP-lowering effect of EA was abolished by the A_2AR antagonist SCH 58261 in the rVLM, but not by the vehicle.
• Microinjection of the A_2AR agonist CGS-21680 into the rVLM decreased BP in sham-EA treated rats, and A_2AR levels in the rVLM were elevated after EA treatment compared to controls.

Conclusions:

• A four-week course of EA treatment effectively lowers BP in salt-sensitive hypertensive rats.
• The findings strongly suggest that the sustained hypotensive effect of EA is mediated, at least in part, by the activation of adenosine A_2AR within the rostral ventrolateral medulla.
• This study elucidates a key neurochemical pathway involved in acupuncture's therapeutic effect on hypertension.