We examined the influence of chronic cocaine exposure, in an unlimited access self-administration paradigm, on density of the dopamine transporter (3H-WIN 35,428 and 3H-GBR 12,935 binding) and concentration of monoamine (dopamine, serotonin, noradrenaline and metabolites) neurotransmitters in rat brain. In normal rodent striatum 3H-WIN 35,428 and 3H-GBR 12,935 binding to the dopamine transporter, although generally similar, showed different subregional rostrocaudal and mediolateral gradients, suggesting that the two ligands might bind to different subtypes or states of the dopamine transporter. Following chronic, unlimited access cocaine self-administration, binding of 3H-WIN 35,428 was significantly elevated in whole nucleus accumbens (+69%, p < 0.001) and striatum (+65%, p < 0.001) on the last day of cocaine exposure ("on-cocaine group"); whereas in the 3 week withdrawn animals ("cocaine-withdrawn group"), levels were either normal (striatum) or reduced (-30%, p < 0.05, nucleus accumbens). Although similar changes in 3H-GBR 12,935 binding were observed, this dopamine transporter ligand showed a smaller and highly subregionally dependent increase in binding in striatal subdivision of the on-cocaine group, but a more marked binding reduction in the cocaine-withdrawn animals. As compared with the controls, mean dopamine levels were reduced in striatum (-15%, p < 0.05) of the on-cocaine group and in nucleus accumbens (-40%, p < 0.05) of the cocaine-withdrawn group. These data provide additional support to the hypothesis that some of the long-term effects of cocaine exposure (drug craving, depression) could be consequent to reduced nucleus accumbens dopamine function. Our data also suggest that dopamine transporter concentration, and perhaps function, might undergo up- or downregulation, either as a direct effect of cocaine, or indirectly as part of a homeostatic response to altered synaptic dopamine levels, and therefore might participate in the neuronal events underlying cocaine-induced behavioral changes.
It has recently been reported that purity of illicit tablets of ecstasy (MDMA) is now high. Our objective was to confirm whether hair of drug users, who request only ecstasy from their supplier, contains MDMA in the absence of other drugs. GC-MS analysis of scalp hair segments disclosed the presence of MDMA in 19 of 21 subjects and amphetamine/methamphetamine in eight subjects. Surprisingly, seven subjects had hair levels of the MDMA metabolite, MDA, equal to or greater than those of MDMA, suggesting use of MDA in addition to that of MDMA. These amphetamine derivatives might be included by clandestine laboratories to enhance effects of the drug cocktail or because of a perception that MDA synthesis might be simpler than that of MDMA. Drug users and investigators examining possible brain neurotoxic effects of MDMA need to consider that "ecstasy" tablets can contain MDA and methamphetamine despite no demand for the drugs.
We measured concentrations of cocaine and its major metabolites (benzoylecgonine, ecgonine methylester, norcocaine, and cocaethylene) in 15 autopsied brain regions of 14 human chronic cocaine users. Only slight differences were observed in concentrations of cocaine and its metabolites amongst the examined brain areas. Although it is likely that some postmortem redistribution of the drug must have occurred, our data are consistent with the possibility that behaviorally relevant doses of cocaine are widely distributed throughout the brain of humans who use the drug on a chronic basis. Consideration should therefore be given to the possible pharmacological and toxicological actions of cocaine in both striatal and extra-striatal brain areas in human users of the drug.
Evidence that the widely used methamphetamine analog MDMA (3,4-methylenedioxymethamphetamine, ecstasy) might damage brain serotonin neurones in humans is derived from imaging investigations showing variably decreased binding of radioligands to the serotonin transporter (SERT), a marker of serotonin neurones. However, in humans, it is not known whether low SERT binding reflects actual loss of SERT protein itself. As this question can only be answered in post-mortem brain, we measured protein levels of SERT and that of the rate-limiting serotonin-synthesizing enzyme tryptophan hydroxylase (TPH) in autopsied brain of a high-dose MDMA user. As compared with control values, SERT protein levels were markedly (−48% to −58%) reduced in striatum (caudate, putamen) and occipital cortex and less affected (−25%) in frontal and temporal cortices, whereas TPH protein was severely decreased in caudate and putamen (−68% and −95%, respectively). The magnitude of the striatal SERT protein reduction was greater than the SERT binding decrease typically reported in imaging studies. Although acknowledging limitations of a case study, these findings extend imaging data based on SERT binding and suggest that high-dose MDMA exposure could cause loss of two key protein markers of brain serotonin neurones, a finding compatible with either physical damage to serotonin neurones or downregulation of components therein.
Despite the increasing incidence of illicit use of gamma-hydroxybutyrate (GHB), little information is available documenting levels of the drug in GHB fatalities. We measured GHB levels in postmortem blood, brain and hair specimens from a suspected overdose case by gas chromatography/mass spectrometry (GC/MS) following solid phase extraction (SPE) and derivatization with bis(trimethyl-silyl) trifluoroacetamide (BSTFA). Examination found 330 microg/mL GHB in femoral blood and 221 ng/mg GHB in frontal cortex brain tissue, values higher than those typically reported in the literature. The hair shaft was negative for GHB whereas the plucked root bulbs with outer root sheath attached (2,221 ng/mg) and root bulbs after washing and removal of the outer root sheath (47 ng/mg) contained the drug. Our results are consistent with an acute single dose of GHB and, as the toxicology screen was negative for other drugs of abuse, emphasize the significant danger of this drug.
