Different response to exogenous L-arginine in nitric oxide production between hippocampus and striatum of conscious rats: a microdialysis study.
We previously showed that systemic administration of a nitric oxide (NO) precursor, L-arginine (L-Arg), failed to reverse suppression by NO synthase (NOS) inhibitors of chemically induced shaking behavior in rats, leading to the hypothesis that exogenous L-Arg might be non-uniformly supplied to brain regions susceptible to NOS inhibitors. In the present study, therefore, we examined the effect of exogenous L-Arg on the extracellular levels of the oxidative nitric oxide (NO) products, nitrite (NO2-) and nitrate (NO3-), in two different brain regions, the hippocampus and the striatum, of conscious rats by means of in vivo brain microdialysis. The basal NO2- levels in the two brain regions were comparable, while the NO3- level was significantly lower in the hippocampus than the striatum. The addition of 10 mM L-Arg, but not D-Arg, to the perfusing solution significantly increased NO2- and NO3- in the hippocampus and NO2- alone in the striatum. These increases were abolished by 1 mM N(omega)-nitro-L-arginine, an NOS inhibitor. L-Arg at 1mM was able to significantly increase NO2-, but not NO3-, in the hippocampus to a level comparable with that at 10 mM L-Arg, while it had no effect in the striatum. L-Arg (500 mg/kg, i.p.) induced a significant increase in NO2- and NO3- in the hippocampus, but not in the striatum. These results suggest that the striatum may have a lower ability to enhance NO production by utilising exogenous L-Arg than the hippocampus, despite higher basal NO production.
Department of Forensic Medicine, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. s-hara@tokyo-med.ac.jp
Shuichi
S
Hara
Toshiji
T
Mukai
Kunihiko
K
Kurosaki
Hajime
H
Mizukami
Fumi
F
Kuriiwa
Takahiko
T
Endo
D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D017551:Microdialysis / Q000379:methods; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology*
D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine