Circadian rhythm of nitric oxide production in the dorsal region of the suprachiasmatic nucleus in rats.
Extracellular concentration of nitrite (NO2-), an oxidized product of nitric oxide (NO), was measured consecutively in the dorsal region of the rat suprachiasmatic nucleus (SCN) by means of in vivo microdialysis. The NO2- concentrations in the dialysates showed robust circadian rhythm under a 12:12 h light/dark cycle and were higher during the dark phase than during the light phase. When the rats were transferred to constant darkness, the 24 h rhythm of NO2- persisted without damping the amplitude. The NO2- level was significantly lowered by an injection of NO synthase inhibitor (NG-monomethyl-L-arginine, 10 mg/kg i.p.). These findings indicate that the daily fluctuation of NO2- in the dorsal region of the SCN, which represents endogenous rhythm of NO, is regulated independently of photic inputs into the SCN and may be related to the circadian clock functions.
Mitome
M
M
Department of Oral Functional Science, Hokkaido University Graduate School of Dental Medicine, N13W7, Kita-ku, 060-8586, Sapporo, Japan. mit@hucc.hokudai.ac.jp
Shirakawa
T
T
Oshima
S
S
Nakamura
W
W
Oguchi
H
H
D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D009043:Motor Activity / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*
D009573:Nitrites; D009569:Nitric Oxide