title: Chronic inhibition of nitric oxide synthase activity by NG-nitro-L-arginine induces nitric oxide synthase expression in the developing rat cerebellum.
abstract: Studies on chronic inhibition of nitric oxide synthase (NOS) in the CNS suggest a plastic change in nitric oxide (NO) synthesis in areas related to motor control, which might protect the animal from the functional and behavioral consequences of NO deficiency. In the present study, the acute and chronic effect of the substrate analogue inhibitor N(G)-nitro-l-arginine (l-NNA) was examined on NO production, NO-sensitive cyclic guanosine monophosphate (cGMP) levels and the expression of NOS isoforms in the developing rat cerebellum. Acute intraperitoneal administration of the inhibitor (5-200mg/kg) to 21-day-old rats reduced NOS activity and NO concentration dose dependently by 70-90% and the tissue cGMP level by 60-80%. By contrast, chronic application of l-NNA between postnatal days 4-21 diminished the total NOS activity and NO concentration only by 30%, and the tissue cGMP level by 10-50%. Chronic treatment of 10mg/kg l-NNA induced neuronal (n)NOS expression in granule cells, as revealed by in situ hybridization, NADPH-diaphorase histochemistry and Western-blot, but it had no significant influence on tissue cGMP level or on layer formation of the cerebellum. However, a higher concentration (50mg/kg) of l-NNA decreased the intensity of the NADPH-diaphorase reaction in granule cells, significantly reduced cGMP production, and retarded layer formation and induced inducible (i)NOS expression & activity in glial cells. Treatments did not affect endothelial (e)NOS expression. The administration of the biologically inactive isomer D-NNA (50mg/kg) or saline was ineffective. The present findings suggest the existence of a concentration-dependent compensatory mechanism against experimentally-induced cronich inhibition of NOS, including nNOS or iNOS up-regulation, which might maintain a steady-state NO level in the developing cerebellum.
authors.affiliation: Department of Experimental Zoology, Balaton Limnological Institute, Center for Ecological Research, Hungarian Academy of Sciences, Klebelsberg Kuno u. 3, H-8237 Tihany, Hungary. serfozo@tres.blki.hu
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Serfőző
authors.forename: Beáta
authors.initials: B
authors.lastname: Lontay
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Kukor
authors.forename: Ferenc
authors.initials: F
authors.lastname: Erdődi
mesh_terms: D000818:Animals; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development*; D002908:Chronic Disease; D004334:Drug Administration Schedule; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019335:Nitroarginine; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat