Spectroscopic and electrochemical studies of cocaine-opioid interactions.

The drugs of abuse cocaine (C), heroin (H), and morphine (M) have been studied to enable understanding of the occurrence of cocaine-opioid interactions at a molecular level. Electrochemical, Raman, and NMR studies of the free drugs and their mixtures were used to study drug-drug interactions. The results were analyzed using data obtained from quantum-mechanical calculations. For the cocaine-morphine mixture (C-MH), formation of a binary complex was detected; this involved the 3-phenolic group and the heterocyclic oxygen of morphine and the carbonyl oxygen and the methyl protons of cocaine's methyl ester group. NMR studies conducted simultaneously also revealed C-MH binding geometry consistent with theoretical predictions and with electrochemical and vibrational spectroscopy results. These results provide evidence for the occurrence of a cocaine-morphine interaction, both in the solid state and in solution, particularly for the hydrochloride form. A slight interaction, in solution, was also detected by NMR for the cocaine-heroin mixture.

Expression of NR1/NR2B N-methyl-D-aspartate receptors enhances heroin toxicity in HEK293 cells.

Repeated use of drugs of abuse, namely opiates, has been shown to affect glutamate-releasing neurons. Moreover, blockade of N-methyl-D-aspartate (NMDA) receptors (NMDAR) prevents cell death by apoptosis induced by morphine, a heroin metabolite. Thus, in this article we investigated the involvement of different NMDAR subunits in heroin cytotoxicity. Human embryonic kidney (HEK293) cells, which do not express native NMDAR, were transfected with NR1/NR2A or NR1/NR2B subunits. As a control, cells were transfected with NR1 alone, which does not form functional channels. Incubation with heroin for 24 h induced a dose-dependent decrease in cell viability both in NR1-transfected and nontransfected cells. The loss of membrane integrity induced by heroin was more evident in cells transfected with NR1/NR2B than in cells transfected with NR1 alone or NR1/NR2A. This decrease in cell viability was blocked by MK-801, a selective and noncompetitive antagonist of NMDAR. Nevertheless, no significant changes in intracellular adenosine 5'-triphosphate (ATP) were observed in cells treated with heroin. These data implicate NR2B-composed NMDAR as important mediators of heroin neurotoxicity.

Influence of the sample preparation method on the serotonin determination in plasma and platelets.

Plasma or platelet serotonin concentration is commonly used to provide information about the serotonergic activity in various psychiatric or neurological diseases. Some difficulties have been described in the measurement of serotonin (5-HT) levels in plasma or platelets. We describe an isocratic liquid-chromatographic assay with amperometric detection for determination of 5-HT in the platelet pellet and in platelet-rich and platelet-poor plasma (PRP and PPP) in sample sizes of 100 microL of plasma. The method uses an RP(18) column and an amperometric detector with a thin-layer type electrochemical fl ow cell, with glassy carbon electrode maintained at a potential of +0.600 V vs an Ag/AgCl reference electrode. Determinations were performed in the presence or in the absence of plasma, since the biological matrix may affect the results. Different validation parameters were analysed: selectivity, accuracy, precision, linearity and stability. Reference values for 5-HT concentration in healthy adults (n = 12) were 6.6 nmol/10(9) platelets, for the platelet pellet, and 5.5 nmol/10(9) platelets, for PRP. The 100 microL sample volume used for the preparation of PPP did not make possible the determination of 5-HT levels with accuracy and precision.