Role of nitric oxide in the nucleus of the solitary tract of rats.
We have determined the role of nitric oxide (NO) in the nucleus of the solitary tract (NTS) of normotensive Wistar rats. The unilateral microinjection of Nomega-nitro-l-arginine methyl ester (10 nmol) to block the synthesis of NO into the NTS significantly decreased the arterial pressure, heart rate (HR) and renal sympathetic nerve activity (RSNA) (-19+/-2 mmHg, -23+/-5 beats/min, -30+/-2%, respectively). The microinjection of carboxy-2-phenyl-4,4,5, 5-tetramethylimidazoline-1-oxyl 3-oxide (Carboxy PTIO) (trapper of NO; 0.1 nmol) into the NTS also decreased arterial pressure and RSNA. Conversely, the microinjection of Et2N[N(O)NO]Na (NOC 18) (NO donor; 10 nmol) caused increases in arterial pressure, HR and RSNA (+14+/-2 mmHg, +11+/-2 beats/min, +38+/-7%, respectively), which was inhibited by the pre-microinjection of Carboxy PTIO (0.1 nmol). On the other hand, not only l-arginine (10 nmol) but also d-arginine (10 nmol), which is inactive to produce NO, significantly decreased the arterial pressure and RSNA. These results suggest that (1) NO acts at the NTS to increase the arterial pressure and RSNA, and (2) the microinjection of l-arginine as well as d-arginine led to decreases in arterial pressure and RSNA that were not mediated by the formation of NO in the NTS.
Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan. matsumk@intmed2.kyushu-u.ac.jp
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Matsumura
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Tsuchihashi
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Kagiyama
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Abe
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Fujishima
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007668:Kidney / Q000294:innervation; D008297:Male; D008845:Microinjections; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D009603:Nitroso Compounds / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects
D001565:Benzoates; D004791:Enzyme Inhibitors; D007093:Imidazoles; C093285:NOC 18; D009603:Nitroso Compounds; C079393:1,3-dihydroxy-4,4,5,5-tetramethyl-2-(4-carboxyphenyl)tetrahydroimidazole; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester