Effect of morphine on striatal dopamine metabolism and ascorbic acid and uric acid release in freely moving rats
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.
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ABSTRACT: More must be learned about metabolic and biochemical alterations that contribute to the development and expression of drug dependence. Experimental opioid administration influences mechanisms and indices of oxidative stress, such as antioxidant compounds and purine metabolism. We examined perturbations of neurotransmitter-related pathways in opioid dependence (OD). In this preliminary study, we used a targeted metabolomics platform to explore whether biochemical changes were associated with OD by comparing OD individuals (n = 14) and non-drug users (n = 10). OD patients undergoing short-term methadone detoxification showed altered oxidation-reduction activity, as confirmed by higher plasma levels of alpha- and gamma-tocopherol and increased GSH/GSSG ratio. OD individuals had also altered purine metabolism, showing increased concentration of guanine and xanthosine, with decreased guanosine, hypoxanthine and hypoxanthine/xanthine and xanthine/xanthosine ratios. Other drug use in addition to opioids was associated with partly different biochemical changes. This is a preliminary investigation using metabolomics and showing multiple peripheral alterations of metabolic pathways in OD. Further studies should explore the metabolic profile of conditions of opioid abuse, withdrawal and long-term abstinence in relation to agonist and antagonist treatment and investigate biochemical signatures of opioid substances and medications.Human Psychopharmacology Clinical and Experimental 12/2009; 24(8):666-75. DOI:10.1002/hup.1068 · 1.85 Impact Factor
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ABSTRACT: Extensive but fragmentary studies have shown: (i) heroin, morphine and opiates are able to induce reactive oxygen species (ROS) formation in several cells, (ii) they decrease the antioxidant defense system including enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and antioxidants, glutathione (GSH), Se, and vitamins. This study is to investigate the oxidative damage to DNA, proteins, and lipids in brain of mice administered heroin via intraperitoneal injection, and the effects of verbascoside and luteolin on this damage. All the indices of oxidative damage, such as 8-hydroxy-2'-deoxyguanosine (8-OHdG), protein carbonyl group and malondialdehyde (MDA) contents increased significantly compared to those of controls in the brains of heroin-administered mice, while the indices related to the in vivo antioxidative capacity, such as the ratio of GSH and oxidized glutathione (GSSG), and activities of SOD, CAT and GPx in the brain, and total antioxidant capacity (TAC) in serum significantly decreased. When heroin-dependent mice were treated with verbascoside or luteolin, oxidative stress status was limited.Pharmazie 08/2005; 60(7):539-43. · 1.00 Impact Factor
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ABSTRACT: In the present study in vivo and ex vivo experiments were combined to evaluate the effects of allopurinol on the neurochemical changes induced by an acute morphine challenge (2 mg kg-1, s.c.). In samples from rat striatum, levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3-methoxytyramine (3-MT), ascorbate (AA), dehydroascorbate (DHAA), hypoxanthine, xanthine and uric acid (UA) were measured. Brain microdialysis experiments were carried out in freely moving rats. Striatal dialysate levels were assayed for DA, DOPAC + HVA, AA and UA using liquid chromatography followed by electrochemical detection. Morphine administration increased the striatal levels of DA metabolites, UA and DHAA and the extracellular concentrations of DA, DOPAC + HVA, UA and AA. Allopurinol (50 mg kg-1 by gavage), an inhibitor of xanthine oxidase which catalyses oxidation of xanthine to UA, decreased basal UA and AA concentrations and the morphine-induced increase in DA metabolites and AA oxidation. Since oxidation of DA and xanthines generates reactive oxygen species (ROS) and AA and UA are the main cellular antioxidants, these findings suggest that: (a) single morphine administration increases DA and xanthine oxidative metabolism with a consequent increase in ROS production, which may account for changes in concentrations of extracellular AA and tissue DHAA; (b) allopurinol decreases morphine-induced DA and xanthine oxidation; (c) UA and AA may act in concert to regulate levels of ROS in the brain.Pharmacological Research 07/1997; 35(6):577-85. DOI:10.1006/phrs.1997.0193 · 3.98 Impact Factor