title: Nitric oxide modulates cardiovascular function in the rat by activating adenosine A2A receptors and inhibiting acetylcholine release in the rostral ventrolateral medulla.
abstract: 1. Nitric oxide (NO), a gas transmitter, modulates many physiological processes, including the central regulation of cardiovascular activity. However, the mechanisms underlying the regulation of cardiovascular activity remain relatively unexplored. In the present study, we hypothesized that central NO-dependent sympathetic inhibition is mediated by activation of adenosine A(2A) receptors (A(2A)R) and inhibition of acetylcholine (ACh) release in the rostral ventrolateral medulla (RVLM). 2. L-Arginine (L-Arg; an NO donor; 100 nmol/100 nL) was microinjected into the RVLM of male Sprague-Dawley rats and heart rate variability (HRV) was assessed as an index of cardiac sympathovagal balance. Following microinjection of L-Arg, decreases were seen in mean arterial pressure (MAP), heart rate (HR) and the ratio of the low- to high-frequency components (LF/HF) of HRV. Pretreatment of rats with SCH58261 (40 pmol/60 nL into the RVLM), a competitive antagonist of the A(2A) R, attenuated these effects. 3. Western blot analysis and ELISA revealed that adenosine and A(2A)R levels increased in the RVLM following L-Arg microinjection, whereas ACh and muscarinic M(1) receptor levels decreased significantly, in parallel with the cardiovascular responses to L-Arg microinjection. The decrease in ACh levels was abolished by SCH58261 pretreatment. 4. Microinjection of N(G)-nitro-L-arginine methyl ester (a non-selective inhibitor of NO synthase; 15 nmol/100 nL) into the RVLM significantly increased MAP, HR and sympathetic activity, as evidenced by HRV (LF, HF and the LF/HF ratio were all increased). 5. The results indicate that the central NO/NO synthase system in the RVLM may modulate cardiovascular activity by activating the A(2A)R, which subsequently inhibits activation of the muscarinic M(1) receptor.
authors: Department of Physiology and Pathophysiology, Shanghai Medical College of Fudan University, China.
authors: Mei-Yan
authors: MY
authors: Jiang
authors: Jun
authors: J
authors: Chen
authors: Jin
authors: J
authors: Wang
authors: Fen
authors: F
authors: Xiao
authors: Huan-Huan
authors: HH
authors: Zhang
authors: Cheng-Rong
authors: CR
authors: Zhang
authors: Dong-Shu
authors: DS
authors: Du
authors: Yin-Xiang
authors: YX
authors: Cao
authors: Lin-Lin
authors: LL
authors: Shen
authors: Da-Nian
authors: DN
authors: Zhu
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D058908:Adenosine A2 Receptor Agonists / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000378:metabolism / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A / Q000378:metabolism*
chemical_list: D058908:Adenosine A2 Receptor Agonists; D043705:Receptor, Adenosine A2A; D009569:Nitric Oxide; D001120:Arginine; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester