Excitation of cells in the rostral medial medulla of the rat by the nitric oxide-cyclic guanosine monophosphate messenger system.
Analgesia has been reported to be facilitated by supraspinal nitric oxide (NO) and cyclic guanosine monophosphate (cGMP). In the rostromedial medulla, an important pain-suppressing region, iontophoretically delivered 8-bromo-cGMP excited most single recorded cells (9/10), and methylene blue (a guanylyl cyclase inhibitor) inhibited all cells (7/7). Nitrite and ferrous ions together, shown voltammetrically ex vivo to yield nitric oxide (NO), excited some cells (14/28) and inhibited others (7/28). Methylene blue blocked excitation (3/3) but not inhibition (4/4) by the putative NO. Spontaneous or glutamate-evoked firing was gradually inhibited (23/32) or unaffected by N omega-nitro-L-arginine (a NO synthase inhibitor), but was mostly inhibited by L-arginine (the NO precursor) (23/26), although a rapid onset militated against elevated NO production. These substances, excepting L-arginine, produced changes consistent with an excitatory cGMP-NO cascade contributing to analgesia.
Hentall
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Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford 61107-1897, USA.
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D006157:Guanosine Monophosphate / Q000502:physiology*; D007501:Iron; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology*; D008751:Methylene Blue; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009573:Nitrites; D019335:Nitroarginine; D011903:Raphe Nuclei / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012394:Rosaniline Dyes; D015290:Second Messenger Systems / Q000502:physiology*
D009573:Nitrites; D012394:Rosaniline Dyes; D019335:Nitroarginine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D006157:Guanosine Monophosphate; D001120:Arginine; C035906:Fast Green; D007501:Iron; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D008751:Methylene Blue