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Effect of morphine on striatal dopamine metabolism and ascorbic and uric acid release in freely moving rats

Enrico, Paolo and Esposito, Giovanni and Mura, Maria A. and Fresu, Luigia Grazia and De Natale, Guglielmo and Miele, Egidio and Desole, Maria Speranza and Miele, Maddalena (1997) Effect of morphine on striatal dopamine metabolism and ascorbic and uric acid release in freely moving rats. Brain Research, Vol. 745 (1-2), p. 173-182. ISSN 0006-8993. Article.

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DOI: 10.1016/S0006-8993(96)01146-8

Abstract

Recent ex vivo findings have shown that morphine increases dopamine (DA) and xanthine oxidative metabolism and ascorbic acid (AA) oxidation in the rat striatum. In the present study, we evaluated the effects of subcutaneous daily morphine (20 mg/kg) administration on DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), AA and uric acid in the striatum of freely moving rats using microdialysis. Dialysates were assayed by high performance liquid chromatography with electrochemical detection. On the first day, morphine administration caused a significant increase in extracellular DA, DOPAC, HVA, AA and uric acid concentrations over a 3 h period after morphine. In all treated rats (n = 7), individual concentrations of DOPAC + HVA were directly correlated with individual AA and uric acid concentrations. Last morphine administration on the 4th day increased DOPAC, HVA, AA and uric acid concentrations but failed to increase those of DA. Individual DOPAC + HVA concentrations were still directly correlated with individual AA and uric acid concentrations. These results suggest that systemic morphine increases both striatal DA release and DA and xanthine oxidative metabolism. Only the former effect undergoes tolerance. The increase in DA oxidative metabolism is highly correlated with that of xanthine. The subsequent enhancement in reactive oxygen species production may account for the increase in extracellular AA.

Item Type:Article
ID Code:4372
Status:Published
Refereed:Yes
Uncontrolled Keywords:Morphine, dopamine xanthine metabolism, ascorbic acid, uric acid, striatum, release in vivo
Subjects:Area 05 - Scienze biologiche > BIO/14 Farmacologia
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze biomediche
001 Università di Sassari > 01 Dipartimenti > Neuroscienze, scienze materno infantili
Publisher:Elsevier
ISSN:0006-8993
Copyright Holders:© 1997 Published by Elsevier Science B.V.
Deposited On:26 Aug 2010 13:50

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