Striatal dopamine, dopamine transporter, and vesicular monoamine transporter in chronic cocaine users
Emory University, Atlanta, Georgia, United States Annals of Neurology
(Impact Factor: 9.98).
09/1996; 40(3):428-39. DOI: 10.1002/ana.410400312
Depletion of striatal dopamine (DA) has been hypothesized to explain some of the neurological and psychiatric complications of chronic use of cocaine, including increased risk for neuroleptic-precipitated movement disorders. We measured levels of DA, as well as two DA nerve terminal indices, namely, the DA transporter (DAT) and the vesicular monoamine transporter (VMAT2) in autopsied brain of 12 chronic cocaine users. Mean DA levels were normal in the putamen, the motor component of the striatum; however 4 of the 12 subjects had DA values below the lower limit of the control range. DA concentrations were significantly reduced in the caudate head (head, -33%; tail, -39%) with a trend for reduction in nucleus accumbens (-27%). Striatal DAT protein (-25 to -46%) and VMAT2 (-17 to -22%) were reduced, whereas DAT determined by [3H]WIN 35,428 binding was normal. In conclusion, our data suggest that chronic cocaine use is associated with modestly reduced levels of striatal DA and the DA transporter in some subjects and that these changes might contribute to the neurological and psychiatric effects of the drug.
Available from: Sharon K. Michelhaugh
- "The abundance of SLC6A3 transcript encoding the DA transporter (a primary determinant of extracellular DA levels and obligatory mediator of cocaine's rewarding effects) was diminished in cocaine abusers, as previously described (Bannon et al, 2002; Little et al, 1998; Zhou et al, 2014). Reduced expression of the TH gene encoding tyrosine hydroxylase (the rate-limiting enzyme in DA production) is consistent with reductions in DA levels reported in chronic cocaine abusers (Wilson et al, 1996). The effect of cocaine on expression of most other genes associated with DA cell phenotype has not been investigated to the same extent. "
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ABSTRACT: Chronic drug abuse, craving, and relapse are thought to be linked to long-lasting changes in neural gene expression arising through transcriptional and chromatin-related mechanisms. The key role that midbrain dopamine (DA)-synthesizing neurons play throughout the addiction process provides a compelling rationale for determining the drug-induced molecular changes that occur in these cells. Yet our understanding of these processes remains rudimentary.Postmortem human brain constitutes a unique resource that can be exploited to gain insights into the pathophysiology of complex disorders such as drug addiction. In this study, we analyzed the profiles of midbrain gene expression in chronic cocaine abusers and well-matched drug-free control subjects using microarray and quantitative PCR. A small number of genes exhibited robust differential expression; many of these are involved in the regulation oftranscription, chromatin, or DA phenotype. Transcript abundances for approximately half of these differentially expressedgeneswere diagnosticfor assigning subjectsto the cocaine-abusing versus control cohort. Identification of a molecular signature associated with pathophysiological changesoccurring in cocaine abusers' midbrains should contribute to the development of biomarkers and novel therapeutic targets for drug addiction.Neuropsychopharmacology accepted article preview online, 19 March 2014; doi:10.1038/npp.2014.70.
Available from: Jay P Mclaughlin
- "HIV-infected, drug-abusing individuals may experience more severe or faster-progressing HIV-1 related neurological impairment (UNAIDS/WHO, 2005). Dopaminergic systems otherwise known to mediate drug reward (Di Chiara et al, 2004; Kalivas and Volkow, 2005; Purohit et al, 2011) may be modified by chronic cocaine use (such as the up-or downregulation of cocaine recognition sites on dopamine (DA) transporters; Malison et al, 1998; Staley et al, 1994; Wilson et al, 1996), and are also implicated in the pathogenesis of HIV-1-associated neurological complications (Berger and Arendt, 2000; Cass et al, 2003). Consistent with this, autopsy of HIV-1 infected brains demonstrates infiltration of HIV-infected cells in DA-rich regions (Navia et al, 1986), and such patients often present comorbid clinical signs common to dopaminergic disorders (Nath, 1999). "
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ABSTRACT: As a major neuropathogenic factor associated with human immunodeficiency virus (HIV) infection, HIV-1 Tat protein is known to synergize with psychostimulant drugs of abuse to cause neurotoxicity and exacerbate the progression of central nervous system pathology. However, the functional consequences of the interaction between HIV-1 Tat and abused drugs on behavior are little known. We tested the hypothesis that HIV-1 Tat expression in brain would modulate the psychostimulant effects of cocaine. Using the GT-tg bigenic mouse model, where brain-selective Tat expression is induced by activation of a doxycycline (Dox) promotor, we tested the effects of Tat on cocaine (10 mg/kg, s.c.) induced locomotion and conditioned place preference (CPP). Compared to uninduced littermates or C57BL/6 J controls, cocaine-induced hyperlocomotion was sustained for a significantly longer duration among Tat-induced mice. Moreover, although all groups displayed similar saline-CPP, Tat-induced GT-tg mice demonstrated a 3-fold increase in cocaine-CPP over the response of either uninduced littermates or Dox-treated C57BL/6 J control mice. Induction of Tat also increased the magnitude of a previously-established cocaine-CPP after an additional cycle of cocaine place conditioning. Despite Tat-induced potentiation, extinction of place preference occurred within 21 days, commensurate with cocaine-extinction among saline-treated littermates and C57BL/6 J controls. Re-exposure to cocaine produced reinstatement of an equivalent place preference in Tat-induced GT-tg, or C57BL/6 J, mice; however, induction of Tat protein after the extinction of CPP also produced reinstatement without additional exposure to cocaine. Together, these data suggest that central HIV-1 Tat expression can potentiate the psychostimulant behavioral effects of cocaine in mice.Neuropsychopharmacology accepted article preview online, 15 August 2013. doi:10.1038/npp.2013.201.
Available from: Joseph Hanig
- "The doses tested in our rat study were selected in order to produce peak serum levels ranging from ~3 to 4-fold above therapeutic levels to those occurring after intentional abuse in humans (Kalasinsky et al., 2001; Wilson et al., 1996b). The 8 h exposure to the stimulants during the rodent's waking period was used to model daily human therapeutic exposures. "
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The meninges (arachnoid and pial membranes) and associated vasculature (MAV) and choroid plexus are important in maintaining cerebrospinal fluid (CSF) generation and flow. MAV vasculature was previously observed to be adversely affected by environmentally-induced hyperthermia (EIH) and more so by a neurotoxic amphetamine (AMPH) exposure. Herein, microarray and RT-PCR analysis was used to compare the gene expression profiles between choroid plexus and MAV under control conditions and at 3 hours and 1 day after EIH or AMPH exposure. Since AMPH and EIH are so disruptive to vasculature, genes related to vasculature integrity and function were of interest.
Our data shows that, under control conditions, many of the genes with relatively high expression in both the MAV and choroid plexus are also abundant in many epithelial tissues. These genes function in transport of water, ions, and solutes, and likely play a role in CSF regulation. Most genes that help form the blood–brain barrier (BBB) and tight junctions were also highly expressed in MAV but not in choroid plexus. In MAV, exposure to EIH and more so to AMPH decreased the expression of BBB-related genes such as Sox18, Ocln, and Cldn5, but they were much less affected in the choroid plexus. There was a correlation between the genes related to reactive oxidative stress and damage that were significantly altered in the MAV and choroid plexus after either EIH or AMPH. However, AMPH (at 3 hr) significantly affected about 5 times as many genes as EIH in the MAV, while in the choroid plexus EIH affected more genes than AMPH. Several unique genes that are not specifically related to vascular damage increased to a much greater extent after AMPH compared to EIH in the MAV (Lbp, Reg3a, Reg3b, Slc15a1, Sct and Fst) and choroid plexus (Bmp4, Dio2 and Lbp).
Our study indicates that the disruption of choroid plexus function and damage produced by AMPH and EIH is significant, but the changes may not be as pronounced as they are in the MAV, particularly for AMPH. Expression profiles in the MAV and choroid plexus differed to some extent and differences were not restricted to vascular related genes.
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