Search

Methamphetamine use disorder (MUD) is characterized by loss of control over compulsive drug use. Here, we used a self-administration (SA) model to investigate transcriptional changes associated with the development of early and late compulsivity during contingent footshocks. Punishment initially separated methamphetamine taking rats into always shock-resistant (ASR) rats that continued active lever pressing and shock-sensitive (SS) rats that reduced their lever pressing. At the end of the punishment phase, rats underwent 15 days of forced abstinence at the end of which they were re-introduced to the SA paradigm followed by SA plus contingent shocks. Interestingly, 36 percent of the initial SS rats developed delayed shock-resistance (DSR). Of translational relevance, ASR rats showed more incubation of methamphetamine craving than DSR and always sensitive (AS) rats. RNA sequencing revealed increased striatal Rab37 and Dipk2b mRNA levels that correlated with incubation of methamphetamine craving. Interestingly, Bdnf mRNA levels showed HDAC2-dependent decreased expression in the AS rats. The present SA paradigm should help to elucidate the molecular substrates of early and late addiction-like behaviors.

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.

In the present study, we analyzed mice with a targeted deletion of β-catenin in DA neurons (DA-βcat KO mice) to address the functional significance of this molecule in the shaping of synaptic responses associated with motor learning and following exposure to drugs of abuse. Relative to controls, DA-βcat KO mice showed significant deficits in their ability to form long-term memories and displayed reduced expression of methamphetamine-induced behavioral sensitization after subsequent challenge doses with this drug, suggesting that motor learning and drug-induced learning plasticity are altered in these mice. Morphological analyses showed no changes in the number or distribution of tyrosine hydroxylase-labeled neurons in the ventral midbrain. While electrochemical measurements in the striatum determined no changes in acute DA release and uptake, a small but significant decrease in DA release was detected in mutant animals after prolonged repetitive stimulation, suggesting a possible deficit in the DA neurotransmitter vesicle reserve pool. However, electron microscopy analyses did not reveal significant differences in the content of synaptic vesicles per terminal, and striatal DA levels were unchanged in DA-βcat KO animals. In contrast, striatal mRNA levels for several markers known to regulate synaptic plasticity and DA neurotransmission were altered in DA-βcat KO mice. This study demonstrates that ablation of β-catenin in DA neurons leads to alterations of motor and reward-associated memories and to adaptations of the DA neurotransmitter system and suggests that β-catenin signaling in DA neurons is required to facilitate the synaptic remodeling underlying the consolidation of long-term memories.

We report that administration of paroxetine, a widely prescribed antidepressant drug that acts by inhibiting reuptake of the neurotransmitter serotonin, suppresses the neurodegenerative process and increases the survival of huntingtin mutant mice, an animal model of Huntington's disease (HD). Paroxetine attenuated motor dysfunction and body weight loss and improved glucose metabolism in the HD mice. Paroxetine was beneficial when treatment was initiated before or after the onset of motor dysfunction, suggesting a potential for such antidepressant drugs in the treatment of presymptomatic and symptomatic HD patients.

3,4‐Methylenedioxymethamphetamine (MDMA, ecstasy) is a popular drug of abuse. MDMA is pharmacologically classified as an entactogen because of its affinities to classical hallucinogens and stimulants. Oral ingestion of a single dose of the drug is associated with euphoria, elevated self‐confidence, and heightened sensory awareness in humans. Evidence for neurotoxicity in the human serotonin (5‐HT) system has been provided. In rats, a single injection of MDMA induces hyperthermia and formation of reactive oxygen species. These effects may cause MDMA‐associated, long‐term 5‐HT depletion, with the cortex being quite sensitive to the biochemical effects of MDMA. It has been suggested that these MDMA effects may be associated with molecular changes in this brain region. To test these ideas, we have made use of the cDNA array analysis, which can provide a more global view of the molecular changes secondary to MDMA injections. Our results show that the genes regulated by MDMA encode proteins that belong to signaling pathways, transcription regulators, or xenobiotic metabolism. Our observations indicate that cortical cells respond to the acute administration of MDMA by modulating transcription of several genes that might lead to long‐term changes in the brain.—Thiriet, N., Ladenheim, B., McCoy, M. T., Cadet, J. L. Analysis of Ecstasy (MDMA) ‐induced transcriptional responses in the rat cortex. FASEB J. 16, 1887–1894 (2002)

Drugs currently used for patients with Parkinson's disease provide temporary relief of symptoms but do not halt or slow the underlying neurodegenerative disease process. Increasing evidence suggests that neurons die in Parkinson's disease by a process called apoptosis, which may be triggered by mitochondrial impairment and oxidative stress. We report that two novel synthetic inhibitors of the tumor suppressor protein p53, pifithrin‐α (PFT‐α) and Z‐1‐117, are highly effective in protecting midbrain dopaminergic neurons and improving behavioral outcome in a mouse model of Parkinson's disease. Mice given intraperitoneal injections of PFT‐α or Z‐1‐117 exhibited improved motor function, reduced damage to nigrostriatal dopaminergic neurons and reduced depletion of dopamine and its metabolites after exposure to the toxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP). MPTP caused an increase in the level of the proapoptotic protein Bax, which was prevented by giving mice PFT‐α and Z‐1‐117. PFT‐α and Z‐1‐117 also suppressed Bax production and apoptosis in cultured dopaminergic cells exposed to MPP+. Our findings demonstrate a pivotal role for p53 in experimental parkinsonism and identify a novel class of synthetic p53 inhibitors with clinical potential.

Amphetamine (AMPH) is a drug of abuse that causes the degeneration of striatal dopamine terminals in mammals. Superoxide radicals seem to participate in AMPH‐induced damage because its toxicity is attenuated in Cu/Zn superoxide dismutase transgenic (SOD‐tg) mice. To provide a detailed analysis of molecular changes associated with AMPH toxicity, we used cDNA arrays consisting of 1176 genes to detect differential changes in gene expression in the striata of wild‐type and SOD‐tg mice treated with neurotoxic doses of the drug. We found 42 genes that showed >1.8‐fold changes in at least two consecutive time points during the course of the study and were differentially affected by AMPH in the two genotypes. Specifically, more transcription factors and genes involved in responses to injury/inflammation were affected in wild‐type mice after AMPH administration. Some of these stimulant‐induced superoxide‐dependent alterations in gene expression might affect neuronal functions and promote neuronal damage. Other changes might help to provide some degree of protection against AMPH toxicity. These results support the view that the use of global array analysis of gene expression will help to identify novel molecular mediators of AMPH‐induced neurodegeneration.—Krasnova, I. N., McCoy, M. T., Ladenheim, B., Cadet, J. L. cDNA array analysis of gene expression profiles in the striata of wild‐type and Cu/Zn superoxide dismutase (SOD) transgenic mice treated with neurotoxic doses of amphetamine. FASEB J.16, 1379–1388 (2002)

Continuous infusion of cocaine or the selective dopamine uptake inhibitors GBR 12909 or RTI‐117 increases locomotor stimulation, to which partial tolerance occurs. In addition, all three drugs produce significant decreases in tyrosine hydroxylase immunoreactivity in caudate putamen and nucleus accumbens core, suggesting a decreased dopaminergic tone. An interaction between cocaine and opioids has long been documented. Chronic cocaine significantly increases μ‐ and κ‐opioid receptors and treatment with a κ‐opioid agonist markedly reduces the behavioral effects of cocaine. In addition, chronic cocaine, but not GBR 12909, increases prodynorphin gene expression in caudate putamen. To further understand the interaction between cocaine and the κ‐opioid system, the effects of a chronic continuous infusion for 14 days of cocaine or one of the selective dopamine uptake inhibitors GBR 12909 or RTI‐117 via osmotic minipump were examined on κ‐opioid receptors using the selective κ‐opioid ligand [3H] U‐69593. [3H] U‐69593 binding density was significantly increased in caudate putamen, nucleus accumbens shell, claustrum, and endopiriform nucleus after cocaine, while neither GBR 12909 nor RTI‐117 had any effect. The increased κ‐opioid receptor densities observed following cocaine are likely not related to dopamine uptake inhibition, since they were not produced by selective dopamine uptake inhibitors. These findings suggest that regulation of κ‐opioid receptors by cocaine may be via inhibition of serotonin or norepinephrine uptake, by a combination of effects on two or three monoamine transporters, or by a mechanism unrelated to transporter inhibition. Synapse 45:153–158, 2002. © 2002 Wiley‐Liss, Inc.

Continuous infusion of cocaine or the selective dopamine uptake inhibitors GBR 12909 or RTI-117 increases locomotor stimulation, to which partial tolerance occurs. In addition, all three drugs produce significant decreases in tyrosine hydroxylase immunoreactivity in caudate putamen and nucleus accumbens core, suggesting a decreased dopaminergic tone. An interaction between cocaine and opioids has long been documented. Chronic cocaine significantly increases μ- and κ-opioid receptors and treatment with a κ-opioid agonist markedly reduces the behavioral effects of cocaine. In addition, chronic cocaine, but not GBR 12909, increases prodynorphin gene expression in caudate putamen. To further understand the interaction between cocaine and the κ-opioid system, the effects of a chronic continuous infusion for 14 days of cocaine or one of the selective dopamine uptake inhibitors GBR 12909 or RTI-117 via osmotic minipump were examined on κ-opioid receptors using the selective κ-opioid ligand [³H] U-69593. [³H] U-69593 binding density was significantly increased in caudate putamen, nucleus accumbens shell, claustrum, and endopiriform nucleus after cocaine, while neither GBR 12909 nor RTI-117 had any effect. The increased κ-opioid receptor densities observed following cocaine are likely not related to dopamine uptake inhibition, since they were not produced by selective dopamine uptake inhibitors. These findings suggest that regulation of κ-opioid receptors by cocaine may be via inhibition of serotonin or norepinephrine uptake, by a combination of effects on two or three monoamine transporters, or by a mechanism unrelated to transporter inhibition. Synapse 45:153–158, 2002. © 2002 Wiley-Liss, Inc.

Methamphetamine (METH) is a drug of abuse which can cause apoptosis and degeneration of monoaminergic terminals in the mammalian brain. c‐fos appears to play a protective role against METH‐induced damage because METH toxicity is exacerbated in c‐fos heterozygous knockout mice. In the present study, we used the comprehensive technique of cDNA array to test the idea that heterozygous c‐fos knockout mice might show differential METH‐induced molecular responses in comparison to wild‐type (WT) animals. Of 1,176 genes examined, the expression of 195 genes in either of the two groups of mice was affected by at least 2‐fold at 2 or 12 h after METH treatment. More genes were either up‐ or downregulated in the WT mice. Moreover, there were substantial differences in the pattern of responses between the two genotypes, with more genes involved in DNA repair and protective processes being upregulated in WT mice after METH administration. These results support the idea that the c‐fos knockout genotype may render the animals unable to trigger multicomponent responses in order to protect against the multifaceted toxic effects of this illicit neurotoxin. Synapse 44:211–226, 2002. © 2002 Wiley‐Liss, Inc.

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.

The neural cell adhesion molecule (N-CAM) is a cell recognition molecule involved in cellular migration, synaptic plasticity, and CNS development. A 105- to 115-kDa isoform of N-CAM (cleaved N-CAM or cN-CAM) is increased in schizophrenia in hippocampus, prefrontal cortex, and CSF. We purified and partially characterized cN-CAM, a putative novel isoform, and confirmed that the first 9 amino acids were identical to exon 1 of N-CAM, without the signal sequence. Analysis of trypsin-digested cN-CAM fragments by matrix-assisted laser desorption ionization on a time-of-flight mass spectrometer (MALDI-TOF) yielded peptides that could be identified as being derived from the first 548 amino acid residues of the expected N-CAM amino acid sequence. Immunological identification with four specific N-CAM antisera directed toward cytoplasmic, secreted, variable alternative spliced exon, or GPI epitopes failed to indicate other known splice variants. Neuraminidase treatment of cN-CAM produced a minor alteration resulting in a faster migrating immunoreactive band, indicating partial glycosylation of cN-CAM. Membranous particles from cytosolic brain extract containing cN-CAM were obtained by ultracentrifugation; however, CSF contained few such particles. cN-CAM and synaptophysin were colocalized on these particles. Both cN-CAM and N-CAM 180 were present in synaptosomal preparations of human brain. Following incubation of synaptosomes or brain tissue without protease inhibitors, N-CAM 180 was degraded and cN-CAM was increased. A cN-CAM-like band was present in human fetal neuronal cultures, but not in fetal astrocyte cultures. Thus, cN-CAM represents a protease- and neuraminidase-susceptible fragment possibly derived by proteolytic cleavage of N-CAM 180. An enlargement in ventricular volume in a group of adult patients with schizophrenia over a 2-year interval was found to be correlated with CSF cN-CAM levels as measured at the time of the initial MRI scan (r = 0.53, P = 0.01). cN-CAM is associated with ventricular enlargement; thus, the release of N-CAM fragments may be part of the pathogenic mechanism of schizophrenia in vulnerable brain regions such as the hippocampus and prefrontal cortex. Alternatively, the increases in cN-CAM in schizophrenia may be a reflection of a more general abnormality in the regulation of proteolysis or of extracellular matrix stability.

Methamphetamine (METH) is a neurodegenerative drug of abuse. Its toxicity is characterized by destruction of monoaminergic terminals and by apoptosis in cortical and striatal cell bodies. Multiple factors appear to control METH neurotoxicity, including free radicals and transcription factors. Here, using cDNA arrays, we show the temporal profile of gene expression patterns in the cortex of mice treated with this drug. We obtained two patterns of changes from 588 genes surveyed. First, an early pattern is characterized by upregulation of transcription factors, including members of the jun family. Second, a delayed pattern includes genes related to cell death and to DNA repair. A number of trophic factors were also activated at the later timepoint. These observations suggest that METH can activate a multigene machinery that participates in the production of its toxic effects. The resulting degenerative effects of the drug are thus the result of a balance between protoxic and antiapoptotic mechanisms triggered by its administration to these animals. These observations are of clinical relevance because of the recent identification of degenerative changes in the brains of METH abusers. Synapse 41:40–48, 2001. © 2001 Wiley‐Liss, Inc.

The delta opioid peptide [D‐Ala2, D‐Leu5]enkephalin (DADLE) has been reported to block the neurotoxicity induced by multiple administrations of a moderate dose of methamphetamine (METH). We examined in this study if DADLE might block the neurotoxicity caused by a single high dose of METH in CD‐1 mice. The levels of dopamine transporter (DAT), tyrosine hydroxylase (TH), major biogenic amines including DA, 5‐hydroxytryptamine (5‐HT), and their metabolites were examined. In addition, since the tumor suppressor p53 has been implicated in the neurotoxicity of METH, this study also examined the levels of p53 mRNA and protein affected by METH and DADLE. METH (25 mg/kg, i.p.) caused significant losses of DAT, TH, DA, 3,4‐dihydroxyphenylacetic acid (DOPAC), and 5‐HT in the striatum within 72 h. The administration of a single dose of DADLE (20 mg/kg, i.p., 30 min before METH) caused a complete blockade of all losses induced by METH except for that of the DA content (a ∼50% blockade). DADLE did not affect the changes of rectal temperature induced by the administration of the high dose of METH. METH increased p53 mRNA in the striatum and the hippocampus of CD‐1 mouse. DADLE abolished the p53 mRNA increase caused by METH. METH tended to increase the p53 protein level at earlier time points. However, METH significantly decreased the p53 protein level by about 30% at the 72‐h time point. DADLE blocked both the increase of p53 mRNA and the decrease of p53 protein caused by METH. These results demonstrate a neuroprotective effect of DADLE against the neuronal damage and the alteration of p53 gene expression caused by a single high dose of METH. The results also indicate an apparent discordance between the protein level of p53 and the neurotoxicity caused by a high dose of METH. Synapse 39:305–312, 2001. Published 2001 Wiley‐Liss, Inc.

ABSTRACT: The present study was conducted to investigate the effects of methamphetamine (METH)‐induced toxicity on brain cortical and striatal antioxidant defense systems. Because METH‐induced toxicity is attenuated in copper/zinc‐superoxide dismutase transgenic (Cu/Zn‐SOD‐Tg) mice, we sought to determine if METH had differential effect on antioxidant enzymes on these mice in comparison to non‐Tg mice. METH (4 × 10 mg/kg) induced a significant decrease in Cu/Zn‐SOD activity in the cortical region without altering striatal enzymatic activity in non‐Tg mice; whereas homozygous SOD‐Tg mice showed a significant increase in the striatum. In addition, METH caused decrease in catalase (CAT) activity in the striatum of non‐Tg mice and significant increase in the cortex of homozygous SOD‐Tg mice. METH also induced decreases in glutathione peroxidase (GSH‐Px) in both cortical and striatal regions of non‐Tg mice and in the striatum of heterozygous SOD‐Tg mice. Lipid peroxidation was increased in both cortices and striata of non‐Tg and heterozygous SOD‐Tg mice, whereas the homozygous SOD‐Tg mice were not affected. These results are discussed in terms of their substantiation of a role for oxygen‐based radicals in METH‐induced toxicity in rodents.

Methamphetamine (METH) has long-lasting neurotoxic effects on the nigrostriatal dopamine (DA) system of rodents. METH-induced neurotoxicity is thought to involve release of DA in presynaptic DA terminals, which is associated with increased formation of oxygen-based free radicals. We have recently shown that METH-induced striatal DA depletion is attenuated in transgenic (Tg) mice that express the human CuZn-superoxide dismutase (SOD) enzyme. That study did not specifically address the issue of loss of DA terminals. In the present study, we have used receptor autoradiographic studies of [125I]RTI-121-labeled DA uptake sites to evaluate the effects of several doses of METH on striatal DA terminals of Non-Tg as well as of heterozygous and homozygous SOD-Tg mice. In Non-Tg mice, METH caused decreases in striatal DA uptake sites in a dose-dependent fashion. The loss of DA terminals was more prominent in the lateral region than in the medial subdivisions of the striatum. In SOD-Tg mice, the loss of DA terminals caused by METH was attenuated in a gene dosage-dependent fashion, with the homozygous mice showing the greatest protection. Female mice were somewhat more resistant than male mice against these deleterious effects of METH. These results provide further evidence for a role of superoxide radicals in the long-term effects of METH. They also suggest the notion of a gender-specific handling of oxidative stress.

Methamphetamine (METH) causes deleterious effects in brain monoaminergic systems. Evidence has accumulated to suggest that these effects may be mediated via the overproduction of the superoxide radicals. We have recently shown that METH-induced dopamine (DA) depletion is attenuated in copper-zinc superoxide dismutase (CuZnSOD) transgenic (Tg) mice. In the present study, we have used receptor autoradiographic studies of [125I]RTI-55 labeled serotonin (5-HT) uptake sites to evaluate the effect of a two dosing schedule (5 mg/kg or 10 mg/kg×4) of METH on striatal 5-HT uptake sites in nontransgenic (Non-Tg), heterozygous (Hetero) and homozygous (Homo) SOD-Tg mice. The low dose caused no significant changes in striatal 5-HT uptake sites in any of the groups. The high dose caused marked decreases (−74%) in striatal 5-HT uptake sites in Non-Tg mice. In contrast, 5-HT uptake sites showed only a 31% decrease in homozygous SOD-Tg mice whereas heterozygous SOD-Tg mice showed 63% depletion. These results show that increased SOD activity can protect against METH-induced neurotoxicity in striatal serotonergic terminals. These data provide further evidence for a role of oxidative stress in the neurotoxic effects of METH.