Search

Perturbations in striatal dopamine (DA) homeostasis might underlie the behavioral and pathobiological consequences of METH use disorder in humans. To identify potential consequences of long-term METH exposure, we modeled the adverse consequence DSM criterion of substance use disorders by giving footshocks to rats that had escalated their intake of METH during a drug self-administration procedure. Next, DA D1 receptor antagonist, SCH23390 was injected. Thereafter, rats were euthanized to measure several indices of the striatal dopaminergic system. Footshocks split the METH rats into two phenotypes: (i) shock-sensitive that decreased their METH-intake and (ii) shock-resistant that continued their METH intake. SCH23390 caused substantial dose-dependent reduction of METH taking in both groups. Stopping SCH23390 caused re-emergence of compulsive METH taking in shock-resistant rats. Compulsive METH takers also exhibited greater incubation of METH seeking than non-compulsive rats during withdrawal from METH SA. Analyses of DA metabolism revealed non-significant decreases (about 35%) in DA levels in resistant and sensitive rats. However, striatal contents of the deaminated metabolites, DOPAL and DOPAC, were significantly increased in sensitive rats. VMAT2 and DAT protein levels were decreased in both phenotypes. Moreover, protein expression levels of the D1-like DA receptor, D5R, and D2-like DA receptors, D3R and D4R, were significantly decreased in the compulsive METH takers. Our results parallel findings in post-mortem striatal tissues of human METH users who develop Parkinsonism after long-term METH intake and support the use of this model to investigate potential therapeutic interventions for METH use disorder. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) use disorder (MUD) is characterized by compulsive and repeated drug taking despite negative life consequences. Large intake of METH in humans and animals is accompanied by dysfunctions in learning and memory processes. The endocannabinoid system (ECS) is known to modulate synaptic plasticity and cognitive functions. In addition, the ECS has been implicated in some of the manifestations of substance use disorders (SUDs). We therefore sought to identify potential changes in the expression of various enzymes and of the receptors (CB1 and CB2) that are members of that system. Herein, we used a model of METH self-administration (SA) that includes a punishment phase (footshocks) that helps to separate rats into a compulsive METH phenotype (compulsive) that continues to take METH and a non-compulsive METH (abstinent) group that suppressed or stopped taking METH. Animals were euthanized 2 h after the last METH SA session and their hippocampi were used to measure mRNA levels of cannabinoid receptors (CB/Cnr), as well as those of synthesizing (DAGL-A, DAGL-B, NAPEPLD) and metabolizing (MGLL, FAAH, PTGS2) enzymes of the endocannabinoid cascade. Non-compulsive rats exhibited significant increased hippocampal expression of CB1/Cnr1 and CB2/Cnr2 mRNAs. mRNA levels of the synthesizing enzyme, DAGL-A, and of the metabolic enzymes, MGLL and FAAH, were also increased. Non-compulsive rats also exhibited a significant decrease in hippocampal Ptgs2 mRNA levels. Taken together, these observations implicate the hippocampal endocannabinoid system in the suppression of METH intake in the presence of adverse consequences. [ABSTRACT FROM AUTHOR]

To identify signaling pathways activated by oxycodone self-administration (SA), Sprague–Dawley rats self-administered oxycodone for 20 days using short—(ShA, 3 h) and long-access (LgA, 9 h) paradigms. Animals were euthanized 2 h after SA cessation and dorsal striata were used in post-mortem molecular analyses. LgA rats escalated their oxycodone intake and separated into lower (LgA-L) or higher (LgA-H) oxycodone takers. LgA-H rats showed increased striatal protein phosphorylation of ERK1/2 and MSK1/2. Histone H3, phosphorylated at serine 10 and acetylated at lysine 14 (H3S10pK14Ac), a MSK1/2 target, showed increased abundance only in LgA-H rats. RT-qPCR analyses revealed increased AMPA receptor subunits, GluA2 and GluA3 mRNAs, in the LgA-H rats. GluA3, but not GluA2, mRNA expression correlated positively with changes in pMSK1/2 and H3S10pK14Ac. These findings suggest that escalated oxycodone SA results in MSK1/2-dependent histone phosphorylation and increases in striatal gene expression. These observations offer potential avenues for interventions against oxycodone addiction. [ABSTRACT FROM AUTHOR]

Rationale: Abuse of the psychostimulant methamphetamine (METH) can cause long-lasting damage to brain monoaminergic systems and is associated with profound mental health problems for users, including lasting cognitive impairments. Animal models of METH exposure have been useful in dissecting the molecular effects of the drug on cognition, but many studies use acute, non-contingent "binge" administrations of METH which do not adequately approximate human METH use. Long-term METH exposure via long-access (LgA) self-administration paradigms has been proposed to more closely reflect human use and induce cognitive impairments. Objective: To better understand the role of contingency and patterns of exposure in METH-induced cognitive impairments, we analyzed behavioral and neurochemical outcomes in adult male rats, comparing non-contingent "binge" METH administration with contingent (LgA) METH self-administration and non-contingent yoked partners. Results: Binge METH (40 mg/kg, i.p., over 1 day) dramatically altered striatal and hippocampal dopamine, DOPAC, 5-HT, 5-HIAA, BDNF, and TrkB 75 days after drug exposure. In contrast, 6-h LgA METH self-administration (cumulative 24.8–48.9 mg METH, i.v., over 16 days) altered hippocampal BDNF in both contingent and yoked animals but reduced striatal 5-HIAA in only contingent animals. Neurochemical alterations following binge METH administration were not accompanied by cognitive deficits in Morris water maze, novel object recognition, or Y-maze tests. However, contingent LgA METH self-administration resulted in impaired spatial memory in the water maze. Conclusions: Overall, substantial differences in neurochemical markers between METH exposure and self-administration paradigms did not consistently translate to deficits in cognitive tasks, highlighting the complexity of correlating METH-induced neurochemical changes with cognitive outcomes. [ABSTRACT FROM AUTHOR]

The transition from occasional to escalated psychostimulant use is accelerated by prior drug exposure. These behavioral observations may be related to long-lasting transcriptional and/or epigenetic changes induced by the drug pre-exposure. Herein, we investigated if a single methamphetamine (METH) injection would enhance METH self-administration (SA) and impact any METH SA-induced epigenetic or transcriptional alterations. We thus injected a single METH dose (10 mg/kg) or saline to rats before training them to self-administer METH or saline. There were three experimental groups in SA experiments: (1) a single saline injection followed by saline SA (SS); (2) a single saline injection followed by METH SA (SM); and (3) a single METH injection followed by METH SA (MM). METH-pretreated rats escalated METH SA earlier and took more METH than saline-pretreated animals. Both groups showed similar incubation of cue-induced METH craving. Because compulsive METH takers and METH-abstinent rats show differences in potassium (K+) channel mRNA levels in their nucleus accumbens (NAc), we wondered if K+ channel expression might also help to distinguish between SM and MM groups. We found increases in mRNA and protein expression of shaker-related voltage-gated K+ channels (Kv1: Kcna1, Kcna3, and Kcna6) and calcium-activated K+ channels (Kcnn1) in the SM compared to MM rats. SM rats also showed decreased DNA methylation at the CpG-rich sites near the promoter region of Kcna1, Kcna3 and Kcnn1 genes in comparison to MM rats. Together, these results provide additional evidence for potentially using K+ channels as therapeutic targets against METH use disorder. [ABSTRACT FROM AUTHOR]

Opioid use disorder (OUD) is characterized by compulsive drug taking despite adverse life consequences. Here, we sought to identify neurobiological consequences associated with the behavioral effects of contingent footshocks administered after escalation of oxycodone self-administration. To reach these goals, Sprague-Dawley rats were trained to self-administer oxycodone for 4 weeks and were then exposed to contingent electric footshocks. This paradigm helped to dichotomize rats into two distinct behavioral phenotypes: (1) those that reduce lever pressing (shock-sensitive) and (2) others that continue lever pressing (shock-resistant) for oxycodone during contingent punishment. The rats were euthanized at 2-h after the last oxycodone plus footshock session. The dorsal striata and prefrontal cortices were dissected for use in western blot and RT-qPCR analyses. All oxycodone self-administration rats showed significant decreased expression of Mu and Kappa opioid receptor proteins only in the dorsal striatum. However, expression of Delta opioid receptor protein was decreased in both brain regions. RT-qPCR analyses documented significant decreases in the expression of c-fos , fosB , fra2 , junB , egr1 , and egr2 mRNAs in the dorsal striatum (but not in PFC) of the shock-sensitive rats. In the PFC, junD expression was reduced in both phenotypes. However, egr3 mRNA expression was increased in the PFC of only shock-resistant rats. These results reveal that, similar to psychostimulants and alcohol, footshocks can dichotomize rats that escalated their intake of oxycodone into two distinct behavioral phenotypes. These animals also show significant differences in the mRNA expression of immediate early genes, mainly, in the dorsal striatum. The increases in PFC egr3 expression in the shock-resistant rats suggest that Egr3 might be involved in the persistence of oxycodone-associated memory under aversive conditions. This punishment-driven model may help to identify neurobiological substrates of persistent oxycodone taking and abstinence in the presence of adverse consequences. [ABSTRACT FROM AUTHOR]

Background Methamphetamine (METH) use disorder is prevalent worldwide. There are reports of sex differences in quantities of drug used and relapses to drug use among individuals with METH use disorder. However, the molecular neurobiology of these potential sex differences remains unknown. Methods We trained rats to self-administer METH (0. 1 mg/kg/infusion, i.v.) on an fixed-ratio-1 schedule for 20 days using two 3-hour daily METH sessions separated by 30-minute breaks. At the end of self-administration training, rats underwent tests of cue-induced METH seeking on withdrawal days 3 and 30. Twenty-four hours later, nucleus accumbens was dissected and then used to measure neuropeptide mRNA levels. Results Behavioral results show that male rats increased the number of METH infusions earlier during self-administration training and took more METH than females. Both male and female rats could be further divided into 2 phenotypes labeled high and low takers based on the degree of escalation that they exhibited during the course of the METH self-administration experiment. Both males and females exhibited incubation of METH seeking after 30 days of forced withdrawal. Females had higher basal mRNA levels of dynorphin and hypocretin/orexin receptors than males, whereas males expressed higher vasopressin mRNA levels than females under saline and METH conditions. Unexpectedly, only males showed increased expression of nucleus accumbens dynorphin after METH self-administration. Moreover, there were significant correlations between nucleus accumbens Hcrtr1 , Hcrtr2 , Crhr2 , and Avpr1b mRNA levels and cue-induced METH seeking only in female rats. Conclusion Our results identify some behavioral and molecular differences between male and female rats that had self-administered METH. Sexual dimorphism in responses to METH exposure should be considered when developing potential therapeutic agents against METH use disorder. [ABSTRACT FROM AUTHOR]

Repeated exposure to the opioid agonist, oxycodone, can lead to addiction. Here, we sought to identify potential neurobiological consequences of withdrawal from escalated and non-escalated oxycodone self-administration in rats. To reach these goals, we used short-access (ShA) (3 h) and long-access (LgA) (9 h) exposure to oxycodone self-administration followed by protracted forced abstinence. After 31 days of withdrawal, we quantified mRNA and protein levels of opioid receptors in the rat dorsal striatum and hippocampus. Rats in the LgA, but not the ShA, group exhibited escalation of oxycodone SA, with distinction of two behavioral phenotypes of relatively lower (LgA-L) and higher (LgA-H) oxycodone takers. Both LgA, but not ShA, phenotypes showed time-dependent increases in oxycodone seeking during the 31 days of forced abstinence. Rats from both LgA-L and LgA-H groups also exhibited decreased levels of striatal mu opioid receptor protein levels in comparison to saline and ShA rats. In contrast, mu opioid receptor mRNA expression was increased in the dorsal striatum of LgA-H rats. Moreover, hippocampal mu and kappa receptor protein levels were both increased in the LgA-H phenotype. Nevertheless, hippocampal mu receptor mRNA levels were decreased in the two LgA groups whereas kappa receptor mRNA expression was decreased in ShA and LgA oxycodone groups. Decreases in striatal mu opioid receptor protein expression in the LgA rats may serve as substrates for relapse to drug seeking because these changes occur in rats that showed incubation of oxycodone seeking. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) addiction is a biopsychosocial disorder that is accompanied by multiple relapses even after prolonged abstinence, suggesting the possibilities of long-lasting maladaptive epigenetic changes in the brain. Here, we show that METH administration produced time-dependent increases in the expression of corticotropin-releasing hormone (Crh/Crf), arginine vasopressin (Avp), and cocaine- and amphetamine-regulated transcript prepropeptide (Cartpt) mRNAs in the rat nucleus accumbens (NAc). Chromatin immunoprecipitation (ChIP) assays revealed that METH increased the abundance of phosphorylated CREB (pCREB) at the promoter of Cartpt but not at Avp or Crh DNA sequences. In contrast, METH produced DNA hypomethylation at sites near the Crh transcription start site (TSS) and at intragenic Avp sequences. METH also increased DNA hydroxymethylation at the Crh TSS and at intragenic Avp sites. In addition, METH increased the protein expression of ten-eleven-translocation enzymes that catalyze DNA hydroxymethylation. Importantly, METH increased TET1 binding at the Crh promoter and increased TET3 binding at Avp intragenic regions. We further tested the role of TET enzymes in METH-induced changes in gene expression by using the TET inhibitor, 1,5-isoquinolinediol (IQD), and found that IQD blocked METH-induced increases in Crh and Avp mRNA expression. Together, these results indicate that METH produced changes in neuropeptide transcription by both activation of the cAMP/CREB pathway and stimulation of TET-dependent DNA hydroxymethylation. These results provide molecular evidence for epigenetic controls of METH-induced changes in the expression of neuropeptides. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) administration alters gene expression in the nucleus accumbens (NAc). We recently demonstrated that an acute METH injection produced prolonged increases in the expression of immediate early genes in the NAc of HDAC2-deficient mice, suggesting that HDAC2 might be an important regulator of gene expression in the rodent brain. Here, we tested the possibility that HDAC2 deletion might also impact METH-induced changes in the expression of various HDAC classes in the NAc. Wild-type (WT) and HDAC2 knockout (KO) mice were given a METH (20 mg/kg) injection, and NAc tissue was collected at 1, 2, and 8 h post treatment. We found that METH decreased HDAC3, HDAC4, HDAC7, HDAC8, and HDAC11 mRNA expression but increased HDAC6 mRNA levels in the NAc of WT mice. In contrast, the METH injection increased HDAC3, HDAC4, HDAC7, HDAC8, and HDAC11 mRNA levels in HDAC2KO mice. These observations suggest that METH may induce large-scale transcriptional changes in the NAc by regulating the expression of several HDACs, in part, via HDAC2-dependent mechanisms since some of the HDACs showed differential responses between the two genotypes. Our findings further implicate HDACs as potential novel therapeutic targets for neurotoxic complications associated with the abuse of certain psychostimulants. [ABSTRACT FROM AUTHOR]

In a rat model of drug craving and relapse, cue-induced drug seeking progressively increases after withdrawal from methamphetamine and other drugs, a phenomenon termed 'incubation of drug craving'. However, current experimental procedures used to study incubation of drug craving do not incorporate negative consequences of drug use, which is a common factor promoting abstinence in humans. Here, we studied whether incubation of methamphetamine craving is observed after suppression of drug seeking by adverse consequences (punishment). We trained rats to self-administer methamphetamine or palatable food for 9 h per day for 14 days; reward delivery was paired with a tone-light cue. Subsequently, for one group within each reward type, 50% of the lever-presses were punished by mild footshock for 9-10 days, whereas for the other group lever-presses were not punished. Shock intensity was gradually increased over time. Next, we assessed cue-induced reward seeking in 1-h extinction sessions on withdrawal days 2 and 21. Response-contingent punishment suppressed extended-access methamphetamine or food self-administration; surprisingly, food-trained rats showed greater resistance to punishment than methamphetamine-trained rats. During the relapse tests, both punished and unpunished methamphetamine- and food-trained rats showed significantly higher cue-induced reward seeking on withdrawal day 21 than on day 2. These results demonstrate that incubation of both methamphetamine and food craving occur after punishment-induced suppression of methamphetamine or palatable food self-administration. Our procedure can be used to investigate mechanisms of relapse to drug and palatable food seeking under conditions that more closely approximate the human condition. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is a widely abused amphetamine analog. Few studies have investigated the molecular effects of METH exposure in adult animals. Herein, we determined the consequences of an injection of METH (10 mg/kg) on transcriptional effects of a second METH (2.5 mg/kg) injection given one month later. We thus measured gene expression by microarray analyses in the nucleus accumbens (NAc) of 4 groups of rats euthanized 2 hours after the second injection: saline-pretreated followed by saline-challenged (SS) or METH-challenged (SM); and METH-pretreated followed by saline-challenged (MS) or METH-challenged (MM). Microarray analyses revealed that METH (2.5 mg/kg) produced acute changes (1.8-fold; P<0.01) in the expression of 412 (352 upregulated, 60 down-regulated) transcripts including cocaine and amphetamine regulated transcript, corticotropin-releasing hormone (Crh), oxytocin (Oxt), and vasopressin (Avp) that were upregulated. Injection of METH (10 mg/kg) altered the expression of 503 (338 upregulated, 165 down-regulated) transcripts measured one month later (MS group). These genes also included Cart and Crh. The MM group showed altered expression of 766 (565 upregulated, 201 down-regulated) transcripts including Avp, Cart, and Crh. The METH-induced increased Crh expression was enhanced in the MM group in comparison to SM and MS groups. Quantitative PCR confirmed the METH-induced changes in mRNA levels. Therefore, a single injection of METH produced long-lasting changes in gene expression in the rodent NAc. The long-term increases in Crh, Cart, and Avp mRNA expression suggest that METH exposure produced prolonged activation of the endogenous stress system. The METH-induced changes in oxytocin expression also suggest the possibility that this neuropeptide might play a significant role in the neuroplastic and affiliative effects of this drug. [ABSTRACT FROM AUTHOR]

Background: METH is an illicit drug of abuse that influences gene expression in the rat striatum. Histone modifications regulate gene transcription. Methods: We therefore used microarray analysis and genome-scale approaches to examine potential relationships between the effects of METH on gene expression and on DNA binding of histone H4 acetylated at lysine 4 (H4K5Ac) in the rat dorsal striatum of METH-naïve and METH-pretreated rats. Results: Acute and chronic METH administration caused differential changes in striatal gene expression. METH also increased H4K5Ac binding around the transcriptional start sites (TSSs) of genes in the rat striatum. In order to relate gene expression to histone acetylation, we binned genes of similar expression into groups of 100 genes and proceeded to relate gene expression to H4K5Ac binding. We found a positive correlation between gene expression and H4K5Ac binding in the striatum of control rats. Similar correlations were observed in METH-treated rats. Genes that showed acute METH-induced increased expression in saline-pretreated rats also showed METH-induced increased H4K5Ac binding. The acute METH injection caused similar increases in H4K5Ac binding in METH-pretreated rats, without affecting gene expression to the same degree. Finally, genes that showed METH-induced decreased expression exhibited either decreases or no changes in H4K5Ac binding. Conclusion: Acute METH injections caused increased gene expression of genes that showed increased H4K5Ac binding near their transcription start sites. [ABSTRACT FROM AUTHOR]

Background: Mutations in the human α-synuclein gene lead to early-onset Parkinson's disease (PD); however, phenotypes of α-synuclein mutant mice vary depending upon the promoter driving transgene expression. Objective: The goal of this study was to characterize behavior and neurochemical alterations in mice expressing mutant (A53T) human α-synuclein, controlled by a neuron-specific Thy-1 promoter. Our data provide important additional phenotypic and biochemical characterization of a previously generated model of PD. Methods: A53T (SNCA) and wild type (WT) littermate mice were evaluated for motor function (rotarod and stride length) and anxiety (elevated plus maze and open field) every 2 weeks. At 24 weeks mice were evaluated in a Comprehensive Lab Animal Monitoring System (CLAMS). A separate cohort of mice were euthanized at 12, 24 and 36 weeks for immunoblot analysis of α-synuclein, dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the striatum, and hypothalamic serotonin and metabolites were measured. Results: SNCA mice display significant motor deficits at 14-18 weeks of age compared to WT mice, which progress over time. CLAMS analysis revealed an increase in activity during the dark phase and a reduction in overall estimated sleep time for SNCA mice compared to WT consistent with clinical reports of sleep abnormalities in PD. A transient change in the levels of DAT appeared at 12 weeks in the striatum and serotonin levels were also altered in the hypothalamus at this time point. Conclusions: This PD model displays consistent and clinically relevant motor and sleep phenotypes. Anxiety phenotypes are consistent with other α-synuclein based PD models yet incongruous with typical clinical symptoms. Early increases in serotonin levels potentially explain reductions in anxiety behaviors and sleep. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) addiction is associated with several neuropsychiatric symptoms. Little is known about the effects of METH on gene expression and epigenetic modifications in the rat nucleus accumbens (NAC). Our study investigated the effects of a non-toxic METH injection (20 mg/kg) on gene expression, histone acetylation, and the expression of the histone acetyltransferase (HAT), ATF2, and of the histone deacetylases (HDACs), HDAC1 and HDAC2, in that structure. Microarray analyses done at 1, 8, 16 and 24 hrs after the METH injection identified METH-induced changes in the expression of genes previously implicated in the acute and longterm effects of psychostimulants, including immediate early genes and corticotropin-releasing factor (Crf). In contrast, the METH injection caused time-dependent decreases in the expression of other genes including Npas4 and cholecystokinin (Cck). Pathway analyses showed that genes with altered expression participated in behavioral performance, cell-to-cell signaling, and regulation of gene expression. PCR analyses confirmed the changes in the expression of c-fos, fosB, Crf, Cck, and Npas4 transcripts. To determine if the METH injection caused post-translational changes in histone markers, we used western blot analyses and identified METH-mediated decreases in histone H3 acetylated at lysine 9 (H3K9ac) and lysine 18 (H3K18ac) in nuclear sub-fractions. In contrast, the METH injection caused time-dependent increases in acetylated H4K5 and H4K8. The changes in histone acetylation were accompanied by decreased expression of HDAC1 but increased expression of HDAC2 protein levels. The histone acetyltransferase, ATF2, showed significant METH-induced increased in protein expression. These results suggest that METH-induced alterations in global gene expression seen in rat NAC might be related, in part, to METH-induced changes in histone acetylation secondary to changes in HAT and HDAC expression. The causal role that HATs and HDACs might play in METH-induced gene expression needs to be investigated further. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2012) 120, 125-134. Abstract Ceruloplasmin (Cp) is a ferroxidase involved in iron metabolism by converting Fe2+ to Fe3+, and by regulating cellular iron efflux. In the ceruloplasmin knockout (CpKO) mouse, the deregulation of iron metabolism results in moderate liver and spleen hemosiderosis, but the impact of Cp deficiency on brain neurochemistry and behavior in this animal model is unknown. We found that in contrast to peripheral tissues, iron levels in the hippocampus are significantly reduced in CpKO mice. Although it does not cause any discernable deficits in motor function or learning and memory, Cp deficiency results in heightened anxiety-like behavior in the open field and elevated plus maze tests. This anxiety phenotype is associated with elevated levels of plasma corticosterone. Previous studies provided evidence that anxiety disorders and long-standing stress are associated with reductions in levels of serotonin (5HT) and brain-derived neurotrophic factor (BDNF) in the hippocampus. We found that levels of 5HT and norepinephrine (NE), and the expression of BDNF and its receptor trkB, are significantly reduced in the hippocampus of CpKO mice. Thus, Cp deficiency causes an anxiety phenotype by a mechanism that involves decreased levels of iron, 5HT, NE, and BDNF in the hippocampus. [ABSTRACT FROM AUTHOR]

Single large doses of methamphetamine (METH) cause endoplasmic reticulum (ER) stress and mitochondrial dysfunctions in rodent striata. The dopamine D1 receptor appears to be involved in these METH-mediated stresses. The purpose of this study was to investigate if dopamine D1 and D2 receptors are involved in ER and mitochondrial stresses caused by singleday METH binges in the rat striatum. Male Sprague-Dawley rats received 4 injections of 10 mg/kg of METH alone or in combination with a putative D1 or D2 receptor antagonist, SCH23390 or raclopride, respectively, given 30 min prior to each METH injection. Rats were euthanized at various timepoints afterwards. Striatal tissues were used in quantitative RT-PCR and western blot analyses. We found that binge METH injections caused increased expression of the pro-survival genes, BiP/ GRP-78 and P58IPK, in a SCH23390-sensitive manner. METH also caused up-regulation of ER-stress genes, Atf2, Atf3, Atf4, CHOP/Gadd153 and Gadd34. The expression of heat shock proteins (HSPs) was increased after METH injections. SCH23390 completely blocked induction in all analyzed ER stress-related proteins that included ATF3, ATF4, CHOP/Gadd153, HSPs and caspase-12. The dopamine D2-like antagonist, raclopride, exerted small to moderate inhibitory influence on some METHinduced changes in ER stress proteins. Importantly, METH caused decreases in the mitochondrial anti-apoptotic protein, Bcl- 2, but increases in the pro-apoptotic proteins, Bax, Bad and cytochrome c, in a SCH23390-sensitive fashion. In contrast, raclopride provided only small inhibition of METH-induced changes in mitochondrial proteins. These findings indicate that METH-induced activation of striatal ER and mitochondrial stress pathways might be more related to activation of SCH23390- sensitive receptors. [ABSTRACT FROM AUTHOR]

Rationale: Repeated injections of cocaine cause blunted responses to acute cocaine challenge-induced increases in the expression of immediate early genes (IEGs). Objectives: The aim of this study was to test if chronic methamphetamine (METH) exposure might cause similar blunting of acute METH-induced increases in IEG expression. Results: Repeated saline or METH injections were given to rats over 14 days. After 1 day of withdrawal, they received a single injection of saline or METH (5 mg/kg). Acute injection of METH increased c-fos, fosB, fra2, junB, Egr1-3, Nr4a1 (Nur77), and Nr4a3 (Nor-1) mRNA levels in the striatum of saline-pretreated rats. Chronic METH treatment alone reduced the expression of AP1, Erg1-3, and Nr4a1 transcription factors below control levels. Acute METH challenge normalized these values in METH-pretreated rats. Unexpectedly, acute METH challenge to METH-pretreated animals caused further decreases in Nr4a2 (Nurr1) mRNA levels. In contrast, the METH challenge caused significant but blunted increases in Nr4a3 and Arc expression in METH-pretreated rats. There were also chronic METH-associated decreases in the expression of cAMP responsive element binding protein (CREB) which modulates IEG expression via activation of the cAMP/PKA/CREB signal transduction pathway. Chronic METH exposure also caused significant decreases in preprotachykinin, but not in prodynorphin, mRNA levels. Conclusions: These results support the accumulated evidence that chronic administration of psychostimulants is associated with blunting of their acute stimulatory effects on IEG expression. The METH-induced renormalization of the expression of several IEGs in rats chronically exposed to METH hints to a potential molecular explanation for the recurrent self-administration of the drug by human addicts. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is an addictive and neurotoxic psychostimulant widely abused in the USA and throughout the world. When administered in large doses, METH can cause depletion of striatal dopamine terminals, with preservation of midbrain dopaminergic neurons. Because alterations in the expression of transcription factors that regulate the development of dopaminergic neurons might be involved in protecting these neurons after toxic insults, we tested the possibility that their expression might be affected by toxic doses of METH in the adult brain. Male Sprague-Dawley rats pretreated with saline or increasing doses of METH were challenged with toxic doses of the drug and euthanized two weeks later. Animals that received toxic METH challenges showed decreases in dopamine levels and reductions in tyrosine hydroxylase protein concentration in the striatum. METH pretreatment protected against loss of striatal dopamine and tyrosine hydroxylase. In contrast, METH challenges caused decreases in dopamine transporters in both saline- and METHpretreated animals. Interestingly, METH challenges elicited increases in dopamine transporter mRNA levels in the midbrain in the presence but not in the absence of METH pretreatment. Moreover, toxic METH doses caused decreases in the expression of the dopamine developmental factors, Shh, Lmx1b, and Nurr1, but not in the levels of Otx2 and Pitx3, in salinepretreated rats. METH pretreatment followed by METH challenges also decreased Nurr1 but increased Otx2 and Pitx3 expression in the midbrain. These findings suggest that, in adult animals, toxic doses of METH can differentially influence the expression of transcription factors involved in the developmental regulation of dopamine neurons. The combined increases in Otx2 and Pitx3 expression after METH preconditioning might represent, in part, some of the mechanisms that served to protect against METH-induced striatal dopamine depletion observed after METH preconditioning. [ABSTRACT FROM AUTHOR]

Unilateral injections of 6-hydroxydopamine into the medial forebrain bundle are used extensively as a model of Parkinson's disease. The present experiments sought to identify genes that were affected in the dopamine (DA)-denervated striatum after 6-hydroxydopamine-induced destruction of the nigrostriatal dopaminergic pathway in the rat. We also examined whether a single injection of methamphetamine (METH) (2.5 mg/kg) known to cause changes in gene expression in the normally DA-innervated striatum could still influence striatal gene expression in the absence of DA. Unilateral injections of 6-hydroxydopamine into the medial forebrain bundle resulted in METH-induced rotational behaviors ipsilateral to the lesioned side and total striatal DA depletion on the lesioned side. This injection also caused decrease in striatal serotonin (5- HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels. DA depletion was associated with increases in 5-HIAA/5-HT ratios that were potentiated by the METH injection. Microarray analyses revealed changes (± 1.7-fold, p<0.025) in the expression of 67 genes on the lesioned side in comparison to the intact side of the saline-treated hemiparkinsonian animals. These include follistatin, neuromedin U, and tachykinin 2 which were up-regulated. METH administration caused increases in the expression of c-fos, Egr1, and Nor-1 on the intact side. On the DA-depleted side, METH administration also increased the expression of 61 genes including Pdgf-d and Cox-2. There were METH-induced changes in 16 genes that were common in the DA-innervated and DA-depleted sides. These include c-fos and Nor-1 which show greater changes on the normal DA side. Thus, the present study documents, for the first time, that METH mediated DA-independent changes in the levels of transcripts of several genes in the DA-denervated striatum. Our results also implicate 5-HT as a potential player in these METH-induced alterations in gene expression because the METH injection also caused significant increases in 5-HIAA/5-HT ratios on the DA-depleted side. [ABSTRACT FROM AUTHOR]

Monoamine neurotransmitters play major roles in regulating a range of brain functions in adults and increasing evidence suggests roles for monoamines in brain development. Here we show that mice lacking the monoamine metabolic enzymes MAO A and MAO B (MAO AB-deficient mice) exhibit diminished proliferation of neural stem cells (NSC) in the developing telencephalon beginning in late gestation [embryonic day (E) 17.5], a deficit that persists in neonatal and adult mice. These mice showed significantly increased monoamine levels and anxiety-like behaviors as adults. Assessments of markers of intermediate progenitor cells (IPC) and mitosis showed that NSC in the subventricular zone (SVZ), but not in the ventricular zone, are reduced in MAO AB-deficient mice. A developmental time course of monoamines in frontal cortical tissues revealed increased serotonin levels as early as E14.5, and a further large increase was found between E17.5 and postnatal day 2. Administration of an inhibitor of serotonin synthesis (parachlorophenylalanine) between E14.5 and E19.5 restored the IPC numbers and SVZ thickness, suggesting the role of serotonin in the suppression of IPC proliferation. Studies of neurosphere cultures prepared from the telencephalon at different embryonic and postnatal ages showed that serotonin stimulates proliferation in wild-type, but not in MAO AB-deficient, NSC. Together, these results suggest that a MAO-dependent long-lasting alteration in the proliferation capacity of NSC occurs late in embryonic development and is mediated by serotonin. Our findings reveal novel roles for MAOs and serotonin in the regulation of IPC proliferation in the developing brain. [ABSTRACT FROM AUTHOR]

Multidrug resistance protein 1a (MDR1a) potentiated methylenedioxymethamphetamine (MDMA)-induced decreases of dopamine (DA) and dopamine transport protein in mouse brain one week after MDMA administration. In the present study, we examined if mdr1a wild-type (mdr1a +/+) and knock-out (mdr1a −/−) mice differentially handle the acute effects of MDMA on the nigrostriatal DA system 0–24 h following a single drug injection. 3-way ANOVA revealed significant 2-way interactions of strain × time ( F5,152 = 32.4, P < 0.001) and strain × dose ( F3,152 = 25.8, P < 0.001) on 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratios in mdr1a +/+ and −/− mice. 0.3–3 h after 10 mg/kg MDMA, DOPAC/DA ratios were increased in mdr1a +/+ mice, but decreased 0.3–1 h after MDMA in mdr1a −/− mice. Twenty-four hours after 10 mg/kg MDMA, DOPAC/DA ratios were increased 600% in mdr1a +/+ mice compared to saline-treated control mice, while in mdr1a −/− mice DOPAC/DA ratios were unchanged. Striatal MDMA and its metabolite, methylenedioxyamphetamine, concentrations by gas chromatography–mass spectrometry were similar in both strains 0.3–4 h after MDMA, discounting the role of MDR1a-facilitated MDMA transport in observed inter-strain differences. Increased DOPAC/DA turnover in mdr1a +/+ mice following MDMA is consistent with the previous report that MDMA neurotoxicity is increased in mdr1a +/+ mice. Increased DA turnover via monoamine oxidase in mdr1a +/+ vs −/− mice might increase exposure to neurotoxic reactive oxygen species. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2010) 114, 323–334. Because the olfactory system plays a major role in food consumption, and because ‘food addiction’ and associated morbidities have reached epidemic proportions, we tested the hypothesis that dietary energy restriction can modify adverse effects of cocaine on behavior and olfactory cellular and molecular plasticity. Mice maintained on an alternate day fasting (ADF) diet exhibited increased baseline locomotion and increased cocaine-sensitized locomotion during cocaine conditioning, despite no change in cocaine conditioned place preference, compared with mice fed ad libitum. Levels of dopamine and its metabolites in the olfactory bulb (OB) were suppressed in mice on the ADF diet compared with mice on the control diet, independent of acute or chronic cocaine treatment. The expression of several enzymes involved in dopamine metabolism including tyrosine hydroxylase, monoamine oxidases A and B, and catechol-O-methyltransferase were significantly reduced in OBs of mice on the ADF diet. Both acute and chronic administration of cocaine suppressed the production of new OB cells, and this effect of cocaine was attenuated in mice on the ADF diet. Cocaine administration to mice on the control diet resulted in up-regulation of OB genes involved in mitochondrial energy metabolism, synaptic plasticity, cellular stress responses, and calcium- and cAMP-mediated signaling, whereas multiple olfactory receptor genes were down-regulated by cocaine treatment. ADF abolished many of the effects of cocaine on OB gene expression. Our findings reveal that dietary energy intake modifies the neural substrates underlying some of the behavioral and physiological responses to repeated cocaine treatment, and also suggest novel roles for the olfactory system in addiction. The data further suggest that modification of dietary energy intake could provide a novel potential approach to addiction treatments. [ABSTRACT FROM AUTHOR]

Methamphetamine (meth) is an illicit psychostimulant that is abused throughout the world. Repeated passive injections of the drug given in a single day or over a few days cause significant and long-term depletion of dopamine and serotonin in the mammalian brain. Because meth self-administration may better mimic some aspects of human drug-taking behaviors, we examined to what extent this pattern of drug treatment might also result in damage to monoaminergic systems in the brain. Rats were allowed to intravenously self-administer meth (yoked control rats received vehicle) 15 hours per day for 8 days before being euthanized at either 24 hours or at 7 and 14 days after cessation of drug taking. Meth self-administration by the rats was associated with a progressive escalation of daily drug intake to 14 mg/kg per day. Animals that selfadministered meth exhibited dose-dependent decreases in striatal dopamine levels during the period of observation. In addition, there were significant reductions in the levels of striatal dopamine transporter and tyrosine hydroxylase proteins. There were also significant decreases in the levels of dopamine, dopamine transporter, and tyrosine hydroxylase in the cortex. In contrast, meth self-administration caused only transient decreases in norepinephrine and serotonin levels in the two brain regions, with these values returning to normal at seven days after cessation of drug taking. Importantly, meth selfadministration was associated with significant dose-dependent increases in glial fibrillary acidic protein in both striatum and cortex, with these changes being of greater magnitude in the striatum. These results suggest that meth self-administration by rats is associated with long-term biochemical changes that are reminiscent of those observed in post-mortem brain tissues of chronic meth abusers. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is an illicit toxic psychostimulant which is widely abused. Its toxic effects depend on the release of excessive levels of dopamine (DA) that activates striatal DA receptors. Inhibition of DA-mediated neurotransmission by the DA D1 receptor antagonist, SCH23390, protects against METH-induced neuronal apoptosis. The initial purpose of the present study was to investigate, using microarray analyses, the influence of SCH23390 on transcriptional responses in the rat striatum caused by a single METH injection at 2 and 4 hours after drug administration. We identified 545 out of a total of 22,227 genes as METH-responsive. These include genes which are involved in apoptotic pathways, endoplasmic reticulum (ER) stress, and in transcription regulation, among others. Of these, a total of 172 genes showed SCH23390-induced inhibition of METH-mediated changes. Among these SCH23390-responsive genes were several genes that are regulated during ER stress, namely ATF3, HSP27, Hmox1, HSP40, and CHOP/Gadd153. The secondary goal of the study was to investigate the role of DA D1 receptor stimulation on the expression of genes that participate in ER stress-mediated molecular events. We thus used quantitative PCR to confirm changes in the METH-responsive ER genes identified by the microarray analyses. We also measured the expression of these genes and of ATF4, ATF6, BiP/GRP78, and of GADD34 over a more extended time course. SCH23390 attenuated or blocked METH-induced increases in the expression of the majority of these genes. Western blot analysis revealed METH-induced increases in the expression of the antioxidant protein, Hmox1, which lasted for about 24 hours after the METH injection. Additionally, METH caused DA D1 receptor-dependent transit of the Hmox1 regulator protein, Nrf2, from cytosolic into nuclear fractions where the protein exerts its regulatory functions. When taken together, these findings indicate that SCH23390 can provide protection against neuronal apoptosis by inhibiting METH-mediated DA D1 receptor-mediated ER stress in the rat striatum. Our data also suggest that METH-induced toxicity might be a useful model to dissect molecular mechanisms involved in ER stress-dependent events in the rodent brain. [ABSTRACT FROM AUTHOR]

Pretreatment with methamphetamine (METH) can attenuate toxicity due to acute METH challenges. The majority of previous reports have focused mainly on the effects of the drug on the striatal dopaminergic system. In the present study, we used a regimen that involves gradual increases in METH administration to rats in order to mimic progressively larger doses of the drug used by some human METH addicts. We found that this METH preconditioning was associated with complete protection against dopamine depletion caused by a METH challenge (5 mg/kg × 6 injections given 1 h apart) in the striatum and cortex. In contrast, there was no preconditioning-mediated protection against METH-induced serotonin depletion in the striatum and hippocampus, with some protection being observed in the cortex. There was also no protection against METH-induced norepinephrine (NE) depletion in the hippocampus. These results indicate that, in contrast to the present dogmas, there might be differences in the mechanisms involved in METH toxicity on monoaminergic systems in the rodent brain. Thus, chronic injections of METH might activate programs that protect against dopamine toxicity without influencing drug-induced pathological changes in serotoninergic systems. Further studies will need to evaluate the cellular and molecular bases for these differential responses. [ABSTRACT FROM AUTHOR]

Pretreatment with methamphetamine (METH) can attenuate toxicity due to acute METH challenges. The majority of previous reports have focused mainly on the effects of the drug on the striatal dopaminergic system. In the present study, we used a regimen that involves gradual increases in METH administration to rats in order to mimic progressively larger doses of the drug used by some human METH addicts. We found that this METH preconditioning was associated with complete protection against dopamine depletion caused by a METH challenge (5 mg/kg x 6 injections given 1 hour apart) in the striatum and cortex. In contrast, there was no preconditioning-mediated protection against METH-induced serotonin depletion in the striatum and hippocampus, with some protection being observed in the cortex. There was also no protection against METH-induced norepinephrine depletion in the hippocampus. These results indicate that, in contrast to the present dogmas, there might be differences in the mechanisms involved in METH toxicity on monoaminergic systems in the rodent brain. Thus, chronic injections of METH might activate programs that protect against dopamine toxicity without influencing drug-induced pathological changes in serotoninergic systems. Further studies will need to evaluate the cellular and molecular bases for these differential responses. [ABSTRACT FROM AUTHOR]

The mesocorticolimbic dopamine (DA) system is implicated in mental health disorders affecting attention, impulse inhibition and other cognitive functions. It has also been involved in the regulation of cortical morphogenesis. The present study uses focal injections of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle of BALB/c mice to examine morphological, behavioral and transcriptional responses to selective DA deficit in the fronto-parietal cortex. Mice that received injections of 6-OHDA on postnatal day 1 (PND1) showed reduction in DA levels in their cortices at PND7. Histological analysis at PND120 revealed increased fronto-cortical width, but decreased width of somatosensory parietal cortex. Open field object recognition suggested impaired response inhibition in adult mice after 6-OHDA treatment. Transcriptional analyses using 17K mouse microarrays showed that such lesions caused up-regulation of 100 genes in the cortex at PND7. Notably, among these genes are Sema3A which plays a repulsive role in axonal guidance, RhoD which inhibits dendritic growth and tubulin β5 microtubule subunit. In contrast, 127 genes were down-regulated, including CCTε and CCTζ that play roles in actin and tubulin folding. Thus, neonatal DA depletion affects transcripts involved in control of cytoskeletal formation and pathway finding, instrumental for normal differentiation and synaptogenesis. The observed gene expression changes are consistent with histological cortical and behavioral impairments in the adult mice treated with 6-OHDA on PND1. Our results point towards specific molecular targets that might be involved in disease process mediated by altered developmental DA regulation. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH), a highly addictive drug, can cause degeneration of monoaminergic terminals and neuronal apoptosis in the mammalian brain. In the present article, we have used serial analysis of gene expression (SAGE) to investigate patterns of gene expression in the striata of rats that were given a neurotoxic dose of the drug. SAGE libraries were generated from animals treated with either saline or METH (40 mg/kg) and sacrificed 2 h later. A total of 315 transcripts were differentially expressed between the two libraries ( P < 0.05), with 179 (56%) being upregulated and 136 (44%) being downregulated by the METH injection. Of these, CAATT enhancer-binding protein homologous protein (CHOP)/GADD153 (growth arrest- and DNA damage-inducible gene 153) was found to be upregulated by about threefold. Analysis of the expression of genes downstream of CHOP (DOCs) revealed significant METH-induced increases in their expression. Because DOC1 is an analog of carbonic anhydrase (CA) which is involved in the interconversion between carbon dioxide and the bicarbonate ion, we also measured the effects of METH on the expression of several CAs. These were significantly upregulated by METH in a time-dependent fashion. These results indicate that METH toxicity is mediated, in part, by drug-induced perturbations of physiological processes that are dependent on normal pH and CO2 homeostasis. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is an illicit drug that causes neuronal apoptosis in the mouse striatum, in a manner similar to the neuronal loss observed in neurodegenerative diseases. In the present study, injections of METH to mice were found to cause the death of enkephalin-positive projection neurons but not the death of neuropeptide Y (NPY)/nitric oxide synthase-positive striatal interneurons. In addition, these METH injections were associated with increased expression of neuropeptide Y mRNA and changes in the expression of the NPY receptors Y1 and Y2. Administration of NPY in the cerebral ventricles blocked METH-induced apoptosis, an effect that was mediated mainly by stimulation of NPY Y2 receptors and, to a lesser extent, of NPY Y1 receptors. Finally, we also found that neuropeptide Y knock-out mice were more sensitive than wild-type mice to METH-induced neuronal apoptosis of both enkephalin- and nitric oxide synthase-containing neurons, suggesting that NPY plays a general neuroprotective role within the striatum. Together, our results demonstrate that neuropeptide Y belongs to the class of factors that maintain neuronal integrity during cellular stresses. Given the similarity between the cell death patterns induced by METH and by disorders such as Huntington's disease, our results suggest that NPY analogs might be useful therapeutic agents against some neurodegenerative processes. [ABSTRACT FROM AUTHOR]

Methamphetamine [METH ("speed")I is an abused psychostimulant that can cause psychotic, cognitive, and psychomotor impairment in humans. These signs and symptoms are thought to be related to dysfunctions in basal ganglionic structures of the brain. To identify possible molecular bases for these clinical manifestations, we first used cDNA microarray technology to measure METH-induced transcriptional responses in the striatum of rats treated with an apoptosis-inducing dose of the drug. METH injection resulted in increased expression of members of the Jun, Egr, and Nurll subfamilies of transcription factors (TF5), changes that were confirmed by quantitative PCR. Because pathways linked to these factors are involved in the up-regulation of Fas ligand (FasL), FasL mRNA was quantified and found to be increased. Immunohistochemical studies also revealed METH-induced increased FasL protein expression in striatal GABAergic neurons that express enkephalin. Moreover, there were METH-mediated increases in calcineurin, as well as shuttling of nuclear factor of activated T cells (NFAT)c3 and NFATc4 from the cytosol to the nucleus of METH- treated rats, mechanisms also known to be involved in FasL regulation. Furthermore, METH induced cleavage of caspase-3 in FasL- and Fas-containing neurons. Finally, the METH-induced changes in the FasL-Fas death pathway were attenuated by pre- treatment with the dopamine Dl receptor antagonist SCH23390, which also caused attenuation of METH-induced apoptosis. These observations indicate that METH causes some of its neurodegenerative effects, in part, via stimulation of the Fas-mediated cell death pathway consequent to FasL up-regulation mediated by activation of multiple TFs. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is an illicit drug that causes neurodegenerative effects in humans. In rodents, METH induces apoptosis of striatal glutamic acid decarboxylase (GAD) -containing neurons. This paper provides evidence that METH-induced cell death occurs consequent to interactions of ER stress and mitochondrial death pathways. Specifically, injections of METH are followed by an almost immediate activation of proteases calpain and caspase-12, events consistent with drug-induced ER stress. Involvement of ER stress was further supported by observations of increases in the expression of GRP78/BiP and CHOP. Participation of the mitochondrial pathway was demonstrated by the transition of AIF, smac/DIABLO, and cytochrome c from mitochondrial into cytoplasmic fractions. These changes occur before the apoptosome-associated pro-caspase-9 cleavage. Effector caspases-3 and -6, but not -7, were cleaved with the initial time of caspase-3 activation occurring before caspase 9 cleavage; this suggests possible earlier cleavage of caspase-3 by caspase-12. These events preceded proteolysis of the caspase substrates DFF-45, lamin A, and PARP in nuclear fractions. These findings indicate that METH causes neuronal apoptosis in part via cross-talks between ER- and mitochondria-generated processes, which cause activation of both caspase-dependent and -independent pathways. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is an illicit drug that is also neurotoxic. Recent studies suggest that in addition to dopamine terminal degeneration in the striatum, METH causes apoptosis in cortical neurons. Earlier, we showed that c-fos knockout mice are more susceptible to the toxic effects of the drug. In order to identify possible pathways related to these differences, we have used cDNA array that provided us with a comprehensive catalog of METH affected genes. In the present study, we report on the effects of METH on the integrin family members that were shown to be involved in intracellular signaling cascades effecting cell survival. We found that, in comparison to wild type animals, c-fos knockout mice have lower baseline levels of the integrins in the cortex. Moreover, METH caused time-dependent decreases in their transcripts in both strains of mice. Quantitative RT-PCR confirmed the changes obtained in cDNA array. These findings are discussed in view of the possible role of integrins in METH-induced toxic effects on the cortical neurons. [ABSTRACT FROM AUTHOR]

Presents a study which focused on amphetamine (AMPH) which induces apoptosis of medium spiny striatal projection via the mitochondria-dependent pathway. Description of AMPH; Effect of AMPH on the striatum; Conclusions and findings of the study.

Addiction is associated with neuroadaptive changes in the brain. In the present paper, we used a model of methamphetamine self-administration during which we used footshocks to divide rats into animals that continue to press a lever to get methamphetamine (shock-resistant) and those that significantly reduce pressing the lever (shock-sensitive) despite the shocks. We trained male Sprague-Dawley rats to self-administer methamphetamine (0.1 mg/kg/infusion) for 9 hours daily for 20 days. Control group self-administered saline. Subsequently, methamphetamine self-administration rats were punished by mild electric footshocks for 10 days with gradual increases in shock intensity. Two hours after stopping behavioral experiments, we euthanized rats and isolated nucleus accumbens (NAc) samples. Affymetrix Array experiments revealed 24 differentially expressed genes between the shock-resistant and shock-sensitive rats, with 15 up- and 9 downregulated transcripts. Ingenuity pathway analysis showed that these transcripts belong to classes of genes involved in nervous system function, behavior, and disorders of the basal ganglia. These genes included prodynorphin (PDYN) and proenkephalin (PENK), among others. Because PDYN and PENK are expressed in dopamine D1- and D2-containing NAc neurons, respectively, these findings suggest that mechanisms, which impact both cell types may play a role in the regulation of compulsive methamphetamine taking by rats. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) is a neurotoxic psychostimulant that causes damage to striatal dopamine (DA) terminals and to non-monoaminergic cells in the striatum (STR) and cortex of rodents. The aim of the present study was to investigate short- and long-term consequences of neurotoxic METH doses on mice behaviors. Male BALB/c mice, 12-14 weeks old, were injected with dl-METH (i.p., 7.5 mg/kg x 4 times, every 2 hours) or saline. Behaviors were accessed at 10 days after drug treatment. METH administration caused significant decreases in responding to object displacement using an Open Field Object Recognition test. In contrast, METH caused increased response to object novelty. There were no drug-induced effects on locomotor activity. Moreover, repeated METH injections resulted in significant decreases in dopamine (DA) levels in the STR, frontal cortex (FC) and olfactory bulb (OB) in mice sacrificed 10 days after drug treatment. Furthermore, as previously reported for the cortex and striatum, METH administration caused marked increases in the number of cells that were positive for TUNEL staining in the OB at 3 days, observations that are indicative of drug-induced enhancement of cell death in that structure. When taken together, these results suggest that METH caused impairments in spatial learning and/or memory as a consequence of its neurodegenerative effects. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) produces increases in the expression of immediate early genes (IEGs) and of histone deacetylase 2 (HDAC2) in the rat nucleus accumbens (NAc). Here, we tested whether HDAC2 deletion influenced the effects of METH on IEG expression in the NAc. Microarray analyses showed no baseline differences in IEG expression between wild-type (WT) and HDAC2 knockout (KO) mice. Quantitative-PCR analysis shows that an acute METH injection produced time-dependent increases in mRNA levels of several IEGs in both genotypes. Interestingly, HDAC2KO mice displayed greater METH-induced increases in Egr1 and Egr2 mRNA levels measured at one hour post-injection. The levels of Fosb, Fra2, Egr1, and Egr3 mRNAs stayed elevated in the HDAC2KO mice 2 hours after the METH injection whereas these mRNAs had normalized in the WT mice. In WT mice, METH caused increased HDAC2 recruitment to the promoters some IEGs at 2 hours post injection. METH-induced prolonged increases in Fosb, Fra2, Egr1, and Egr3 mRNA levels in HDAC2KO mice were associated with increased enrichment of phosphorylated CREB (pCREB) on the promoters of these genes. Based on our observations, we hypothesize that HDAC2 may regulate the expression of these genes, in part, by prolonging the actions of pCREB in the mouse NAc. [ABSTRACT FROM AUTHOR]

AbstractAlthough the cause of Parkinson's disease (PD) is unknown, data suggest roles for environmental factors that may sensitize dopaminergic neurons to age-related dysfunction and death. Based upon epidemiological data suggesting roles for dietary factors in PD and other age-related neurodegenerative disorders, we tested the hypothesis that dietary folate can modify vulnerability of dopaminergic neurons to dysfunction and death in a mouse model of PD. We report that dietary folate deficiency sensitizes mice to MPTP-induced PD-like pathology and motor dysfunction. Mice on a folate-deficient diet exhibit elevated levels of plasma homocysteine. When infused directly into either the substantia nigra or striatum, homocysteine exacerbates MPTP-induced dopamine depletion, neuronal degeneration and motor dysfunction. Homocysteine exacerbates oxidative stress, mitochondrial dysfunction and apoptosis in human dopaminergic cells exposed to the pesticide rotenone or the pro-oxidant Fe2+ . The adverse effects of homocysteine on dopaminergic cells is ameliorated by administration of the antioxidant uric acid and by an inhibitor of poly (ADP-ribose) polymerase. The ability of folate deficiency and elevated homocysteine levels to sensitize dopaminergic neurons to environmental toxins suggests a mechanism whereby dietary folate may influence risk for PD. [ABSTRACT FROM AUTHOR]