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Role of endogenous melatonin in the oxidative homeostasis of the extracellular striatal compartment: a microdialysis study in PC12 cells in vitro and in the striatum of freely moving rats

Rocchitta, Gaia Giovanna Maria and Migheli, Rossana and Mura, Maria P. and Esposito, Giovanni and Marchetti, Bianca Maria and Desole, Maria Speranza and Miele, Egidio and Serra, Pier Andrea (2005) Role of endogenous melatonin in the oxidative homeostasis of the extracellular striatal compartment: a microdialysis study in PC12 cells in vitro and in the striatum of freely moving rats. Journal of Pineal Research, Vol. 39 (4), p. 409-418. eISSN 1600-079X. Article.

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DOI: 10.1111/j.1600-079X.2005.00266.x

Abstract

A capillary apparatus for in vitro microdialysis was used to investigate melatonin and ascorbic acid effects on dopamine (DA) autoxidation or nitric oxide (NO)-mediated oxidation in suspended PC12 cells. Following high K+ (KCl 75 mm) infusion, secreted DA underwent a partial autoxidation or peroxynitrite-mediated oxidation when the potential peroxynitrite generator 3-morpholinosydnonimine (SIN-1, 1.0 mm) was co-infused with KCl. Ascorbic acid was supplied to the medium by means of intracellular reduction of infused dehydroascorbic acid (DHAA) (5.0 mm). Melatonin (50 μm) and DHAA showed a synergistic effect in inhibiting DA autoxidation and peroxynitrite-mediated DA oxidation. Moreover, melatonin increased dialysate recovery of ascorbic acid released from PC12 cells. Endogenous melatonin was depleted in rats maintained on a 24-hr light cycle for 1 wk. In melatonin-depleted rats, baseline levels of dialysate ascorbic acid were lower than controls, while those of DA were unaffected. In these rats, intrastriatal infusion of 5.0 mmSIN-1 induced DA increases significantly lower than in controls; in addition, dialysate ascorbic acid concentrations exhibited significant decreases. Melatonin co-infusion restored SIN-1 effects on dialysate DA and antagonized SIN-1-induced ascorbic acid decreases. Melatonin-depleted rats were allowed to recover. In these rats, striatal baseline ascorbic acid, as well as SIN-1-induced increases in dialysate DA did not differ from controls. Taken together, these findings suggest that endogenous melatonin is an active component of the striatal extracellular antioxidant pool, as it maintains endogenous ascorbic acid in its reduced status and co-operates with ascorbic acid in protecting extracellular DA from exogenous NO-mediated oxidation.

Item Type:Article
ID Code:622
Status:Published
Refereed:Yes
Uncontrolled Keywords:Ascorbic acid, endogenous melatonin, extracellular oxidation, nitric oxide, striatal dopamine
Subjects:Area 05 - Scienze biologiche > BIO/14 Farmacologia
Divisions:001 Università di Sassari > 01 Dipartimenti > Neuroscienze, scienze materno infantili
Publisher:Blackwell / Wiley
eISSN:1600-079X
Deposited On:18 Aug 2009 10:02

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