Orexin Receptor-1 in the Rostral Ventrolateral Medulla Mediates the Antihypertensive Effects of Electroacupuncture

Abstract

Electroacupuncture (EA) has been used to treat numerous diseases, including hypertension. This study aimed to investigate the long-term effect and underlying mechanisms of EA stimulation at the LI11 point on the hypertension and sympathetic nerve activity in two-kidney, one-clip (2K1C) hypertensive rats. EA (0.1–0.4 mA, 2 and 15 Hz) was applied to the acupoints LI11 overlying the deep radial nerve once a day for 6 weeks. The mean arterial pressure (MAP) and heart rate (HR) were determined by radiotelemetry, and the sympathetic nerve activity was evaluated by telemetric analyses of the low-frequency component of blood pressure (BP) and by plasma epinephrine and norepinephrine levels. The results showed 6 weeks of EA significantly lowered the increased BP effectively, inhibited the enhanced sympathetic nerve activities and attenuated cardiac hypertrophy in 2K1C hypertensive rats. The level of orexin receptor-1 (OX1R) in the rostral ventrolateral medulla (RVLM) after EA treatment was markedly reduced in 2K1C rats, while there was no difference in the RVLM expression of orexin receptor-2 (OX2R) in 2K1C and 2K1C+EA rats. Moreover, the increased pressor and depressor responses to microinjection of orexin A or OX1R antagonist SB408124 into the RVLM of 2K1C rats were significantly blunted by the EA treatment. These findings suggest that BP-lowering effect of EA on renovascular hypertension may be through inhibition of central sympathetic activities and modulation of functional orexin receptors in the RVLM.

Involvement of Neuropeptide Y within Paraventricular Nucleus in Electroacupuncture Inhibiting Sympathetic Activities in Hypertensive Rats

“…SD rats were implanted with a radiotelemetry system for conscious BP measurements as reported previously [ 20 ]. Rats were briefly anesthetized with 3% isoflurane inhalation.…”

“…The 2K1C hypertension model was produced following our previous report [ 20 , 21 ]. In simple terms, the rats were anesthetized with pentobarbital (i.p., 40 mg/kg), followed by exposing the right kidney via a retroperitoneal flank incision under sterile surgical condition.…”

“…Power spectral analysis of BP variability was performed to assess the changes in sympathetic nerve activity as previously described [ 20 ]. Arterial BP recordings collected from the radiotelemetry system at a sampling rate of 500 Hz and 2 h of continuous recordings for each rat were analyzed using MATLAB software (MathWorks, Natick, MA, United States).…”

“…), and the brain tissues were collected and cut into 500 μ m coronal sections. PVN tissues were dissected by punch-out technique as previously described [ 20 ], and pieces of cerebral cortex from the same section were also obtained. Total RNA from PVN and cerebral cortex was isolated in accordance with the procedure of the RNeasy kit (Qiagen, Valencia, CA, United States).…”